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 $194.96   6.515%   $207.6616   $207.66   $207.65   $207.70  
  Purchase #2 $213.59   8.182%   $231.0659   $231.07   $231.05   $231.10  
  Purchase #3 $19.45   11.195%   $21.6274   $21.63   $21.65   $21.60  
  Purchase #4 $97.37   7.252%   $104.4313   $104.43   $104.45   $104.40  
  Purchase #5 $195.69   8.209%   $211.7542   $211.75   $211.75   $211.80  
  Purchase #6 $148.64   9.123%   $162.2004   $162.20   $162.20   $162.20  
  Purchase #7 $13.26   7.713%   $14.2827   $14.28   $14.30   $14.30  
  7 purchase totals = $882.96       $953.0235   $953.02   $953.05   $953.10