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 $182.68   6.661%   $194.8483   $194.85   $194.85   $194.80  
  Purchase #2 $132.35   8.390%   $143.4542   $143.45   $143.45   $143.50  
  Purchase #3 $130.49   8.642%   $141.7669   $141.77   $141.75   $141.80  
  Purchase #4 $93.67   13.449%   $106.2677   $106.27   $106.25   $106.30  
  Purchase #5 $162.41   6.306%   $172.6516   $172.65   $172.65   $172.70  
  Purchase #6 $189.81   5.420%   $200.0977   $200.10   $200.10   $200.10  
  Purchase #7 $46.88   9.820%   $51.4836   $51.48   $51.50   $51.50  
  7 purchase totals = $938.29       $1,010.5700   $1,010.57   $1,010.55   $1,010.70