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 $23.55   11.169%   $26.1803   $26.18   $26.20   $26.20  
  Purchase #2 $62.51   4.448%   $65.2904   $65.29   $65.30   $65.30  
  Purchase #3 $102.52   4.168%   $106.793   $106.79   $106.80   $106.80  
  Purchase #4 $43.36   11.585%   $48.3833   $48.38   $48.40   $48.40  
  Purchase #5 $153.68   12.832%   $173.4002   $173.40   $173.40   $173.40  
  Purchase #6 $45.92   5.841%   $48.6022   $48.60   $48.60   $48.60  
  Purchase #7 $218.63   12.438%   $245.8232   $245.82   $245.80   $245.80  
  7 purchase totals = $650.17       $714.4726   $714.46   $714.50   $714.50