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 $141.97   9.706%   $155.7496   $155.75   $155.75   $155.70  
  Purchase #2 $235.44   13.507%   $267.2409   $267.24   $267.25   $267.20  
  Purchase #3 $230.61   10.478%   $254.7733   $254.77   $254.75   $254.80  
  Purchase #4 $227.79   5.561%   $240.4574   $240.46   $240.45   $240.50  
  Purchase #5 $132.85   5.804%   $140.5606   $140.56   $140.55   $140.60  
  Purchase #6 $63.54   4.626%   $66.4794   $66.48   $66.50   $66.50  
  Purchase #7 $86.91   9.315%   $95.0057   $95.01   $95.00   $95.00  
  7 purchase totals = $1,119.11       $1,220.2669   $1,220.27   $1,220.25   $1,220.30