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 $212.73   9.323%   $232.5628   $232.56   $232.55   $232.60  
  Purchase #2 $58.98   11.807%   $65.9438   $65.94   $65.95   $65.90  
  Purchase #3 $149.55   8.237%   $161.8684   $161.87   $161.85   $161.90  
  Purchase #4 $178.45   5.752%   $188.7144   $188.71   $188.70   $188.70  
  Purchase #5 $97.67   6.759%   $104.2715   $104.27   $104.25   $104.30  
  Purchase #6 $173.28   12.309%   $194.609   $194.61   $194.60   $194.60  
  Purchase #7 $162.34   7.647%   $174.7541   $174.75   $174.75   $174.80  
  7 purchase totals = $1,033.00       $1,122.7240   $1,122.71   $1,122.65   $1,122.80