Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $176.75   11.832%   $197.6631   $197.66   $197.65   $197.70  
  Purchase #2 $180.91   7.144%   $193.8342   $193.83   $193.85   $193.80  
  Purchase #3 $242.43   10.670%   $268.2973   $268.30   $268.30   $268.30  
  Purchase #4 $182.35   11.766%   $203.8053   $203.81   $203.80   $203.80  
  Purchase #5 $156.48   9.814%   $171.8369   $171.84   $171.85   $171.80  
  Purchase #6 $153.29   4.261%   $159.8217   $159.82   $159.80   $159.80  
  Purchase #7 $115.37   10.389%   $127.3558   $127.36   $127.35   $127.40  
  7 purchase totals = $1,207.58       $1,322.6143   $1,322.62   $1,322.60   $1,322.60