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 $62.49   10.766%   $69.2177   $69.22   $69.20   $69.20  
  Purchase #2 $216.53   5.610%   $228.6773   $228.68   $228.70   $228.70  
  Purchase #3 $143.63   9.426%   $157.1686   $157.17   $157.15   $157.20  
  Purchase #4 $223.42   6.514%   $237.9736   $237.97   $237.95   $238.00  
  Purchase #5 $95.52   7.267%   $102.4614   $102.46   $102.45   $102.50  
  Purchase #6 $243.74   8.726%   $265.0088   $265.01   $265.00   $265.00  
  Purchase #7 $142.88   7.608%   $153.7503   $153.75   $153.75   $153.80  
  7 purchase totals = $1,128.21       $1,214.2577   $1,214.26   $1,214.20   $1,214.40