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 $162.50   6.874%   $173.6703   $173.67   $173.65   $173.70  
  Purchase #2 $165.96   9.865%   $182.332   $182.33   $182.35   $182.30  
  Purchase #3 $64.79   8.159%   $70.0762   $70.08   $70.10   $70.10  
  Purchase #4 $91.59   4.438%   $95.6548   $95.65   $95.65   $95.70  
  Purchase #5 $19.48   5.710%   $20.5923   $20.59   $20.60   $20.60  
  Purchase #6 $148.95   4.112%   $155.0748   $155.07   $155.05   $155.10  
  Purchase #7 $41.38   7.733%   $44.5799   $44.58   $44.60   $44.60  
  7 purchase totals = $694.65       $741.9803   $741.97   $742.00   $742.10