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 $85.55   9.536%   $93.708   $93.71   $93.70   $93.70  
  Purchase #2 $98.30   3.299%   $101.5429   $101.54   $101.55   $101.50  
  Purchase #3 $171.97   6.396%   $182.9692   $182.97   $182.95   $183.00  
  Purchase #4 $134.25   8.370%   $145.4867   $145.49   $145.50   $145.50  
  Purchase #5 $126.58   12.299%   $142.1481   $142.15   $142.15   $142.10  
  Purchase #6 $120.84   13.378%   $137.006   $137.01   $137.00   $137.00  
  Purchase #7 $87.84   5.629%   $92.7845   $92.78   $92.80   $92.80  
  7 purchase totals = $825.33       $895.6454   $895.65   $895.65   $895.60