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 $221.46   4.759%   $231.9993   $232.00   $232.00   $232.00  
  Purchase #2 $211.42   6.699%   $225.583   $225.58   $225.60   $225.60  
  Purchase #3 $191.46   4.339%   $199.7674   $199.77   $199.75   $199.80  
  Purchase #4 $105.95   10.353%   $116.919   $116.92   $116.90   $116.90  
  Purchase #5 $67.84   9.845%   $74.5188   $74.52   $74.50   $74.50  
  Purchase #6 $123.71   12.303%   $138.93   $138.93   $138.95   $138.90  
  Purchase #7 $206.77   4.781%   $216.6557   $216.66   $216.65   $216.70  
  7 purchase totals = $1,128.61       $1,204.3732   $1,204.38   $1,204.35   $1,204.40