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 $177.89   4.282%   $185.5072   $185.51   $185.50   $185.50  
  Purchase #2 $196.28   10.857%   $217.5901   $217.59   $217.60   $217.60  
  Purchase #3 $60.56   13.669%   $68.8379   $68.84   $68.85   $68.80  
  Purchase #4 $209.50   11.166%   $232.8928   $232.89   $232.90   $232.90  
  Purchase #5 $246.61   5.521%   $260.2253   $260.23   $260.25   $260.20  
  Purchase #6 $156.52   8.431%   $169.7162   $169.72   $169.70   $169.70  
  Purchase #7 $55.95   8.581%   $60.7511   $60.75   $60.75   $60.80  
  7 purchase totals = $1,103.31       $1,195.5206   $1,195.53   $1,195.55   $1,195.50