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 $55.80   12.544%   $62.7996   $62.80   $62.80   $62.80  
  Purchase #2 $176.52   9.522%   $193.3282   $193.33   $193.35   $193.30  
  Purchase #3 $170.54   9.374%   $186.5264   $186.53   $186.55   $186.50  
  Purchase #4 $126.84   9.700%   $139.1435   $139.14   $139.15   $139.10  
  Purchase #5 $180.69   5.781%   $191.1357   $191.14   $191.15   $191.10  
  Purchase #6 $181.32   12.632%   $204.2243   $204.22   $204.20   $204.20  
  Purchase #7 $231.45   4.164%   $241.0876   $241.09   $241.10   $241.10  
  7 purchase totals = $1,123.16       $1,218.2453   $1,218.25   $1,218.30   $1,218.10