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 $244.71   5.329%   $257.7506   $257.75   $257.75   $257.80  
  Purchase #2 $171.95   13.198%   $194.644   $194.64   $194.65   $194.60  
  Purchase #3 $40.99   4.566%   $42.8616   $42.86   $42.85   $42.90  
  Purchase #4 $168.36   5.620%   $177.8218   $177.82   $177.80   $177.80  
  Purchase #5 $84.64   10.502%   $93.5289   $93.53   $93.55   $93.50  
  Purchase #6 $180.65   6.151%   $191.7618   $191.76   $191.75   $191.80  
  Purchase #7 $190.46   6.580%   $202.9923   $202.99   $203.00   $203.00  
  7 purchase totals = $1,081.76       $1,161.3610   $1,161.35   $1,161.35   $1,161.40