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 $174.73   7.206%   $187.321   $187.32   $187.30   $187.30  
  Purchase #2 $60.32   5.224%   $63.4711   $63.47   $63.45   $63.50  
  Purchase #3 $239.69   6.302%   $254.7953   $254.80   $254.80   $254.80  
  Purchase #4 $46.95   7.507%   $50.4745   $50.47   $50.45   $50.50  
  Purchase #5 $101.51   5.459%   $107.0514   $107.05   $107.05   $107.10  
  Purchase #6 $61.68   6.284%   $65.556   $65.56   $65.55   $65.60  
  Purchase #7 $153.67   10.166%   $169.2921   $169.29   $169.30   $169.30  
  7 purchase totals = $838.55       $897.9614   $897.96   $897.90   $898.10