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 $62.33   4.360%   $65.0476   $65.05   $65.05   $65.00  
  Purchase #2 $166.88   5.265%   $175.6662   $175.67   $175.65   $175.70  
  Purchase #3 $249.93   10.239%   $275.5203   $275.52   $275.50   $275.50  
  Purchase #4 $186.25   6.112%   $197.6336   $197.63   $197.65   $197.60  
  Purchase #5 $71.51   6.198%   $75.9422   $75.94   $75.95   $75.90  
  Purchase #6 $69.46   13.349%   $78.7322   $78.73   $78.75   $78.70  
  Purchase #7 $170.52   9.806%   $187.2412   $187.24   $187.25   $187.20  
  7 purchase totals = $976.88       $1,055.7833   $1,055.78   $1,055.80   $1,055.60