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 $88.36   7.526%   $95.01   $95.01   $95.00   $95.00  
  Purchase #2 $42.89   8.340%   $46.467   $46.47   $46.45   $46.50  
  Purchase #3 $39.93   9.434%   $43.697   $43.70   $43.70   $43.70  
  Purchase #4 $245.30   4.403%   $256.1006   $256.10   $256.10   $256.10  
  Purchase #5 $52.25   9.713%   $57.325   $57.33   $57.35   $57.30  
  Purchase #6 $46.28   8.289%   $50.1161   $50.12   $50.10   $50.10  
  Purchase #7 $180.84   6.297%   $192.2275   $192.23   $192.25   $192.20  
  7 purchase totals = $695.85       $740.9432   $740.96   $740.95   $740.90