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 $88.77   9.317%   $97.0407   $97.04   $97.05   $97.00  
  Purchase #2 $85.61   12.642%   $96.4328   $96.43   $96.45   $96.40  
  Purchase #3 $100.51   6.172%   $106.7135   $106.71   $106.70   $106.70  
  Purchase #4 $48.45   9.859%   $53.2267   $53.23   $53.25   $53.20  
  Purchase #5 $87.83   8.163%   $94.9996   $95.00   $95.00   $95.00  
  Purchase #6 $6.73   11.763%   $7.5216   $7.52   $7.50   $7.50  
  Purchase #7 $207.78   5.419%   $219.0396   $219.04   $219.05   $219.00  
  7 purchase totals = $625.68       $674.9745   $674.97   $675.00   $674.80