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 $38.91   12.388%   $43.7302   $43.73   $43.75   $43.70  
  Purchase #2 $59.26   4.817%   $62.1146   $62.11   $62.10   $62.10  
  Purchase #3 $94.38   11.214%   $104.9638   $104.96   $104.95   $105.00  
  Purchase #4 $174.75   10.424%   $192.9659   $192.97   $192.95   $193.00  
  Purchase #5 $209.93   6.200%   $222.9457   $222.95   $222.95   $222.90  
  Purchase #6 $104.71   9.845%   $115.0187   $115.02   $115.00   $115.00  
  Purchase #7 $171.92   13.790%   $195.6278   $195.63   $195.65   $195.60  
  7 purchase totals = $853.86       $937.3667   $937.37   $937.35   $937.30