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 $199.52   12.622%   $224.7034   $224.70   $224.70   $224.70  
  Purchase #2 $223.81   7.785%   $241.2336   $241.23   $241.25   $241.20  
  Purchase #3 $59.78   8.663%   $64.9587   $64.96   $64.95   $65.00  
  Purchase #4 $102.44   11.251%   $113.9655   $113.97   $113.95   $114.00  
  Purchase #5 $192.90   12.638%   $217.2787   $217.28   $217.30   $217.30  
  Purchase #6 $229.53   11.782%   $256.5732   $256.57   $256.55   $256.60  
  Purchase #7 $68.56   12.125%   $76.8729   $76.87   $76.85   $76.90  
  7 purchase totals = $1,076.54       $1,195.5860   $1,195.58   $1,195.55   $1,195.70