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 $68.52   7.528%   $73.6782   $73.68   $73.70   $73.70  
  Purchase #2 $247.80   8.405%   $268.6276   $268.63   $268.65   $268.60  
  Purchase #3 $75.42   8.866%   $82.1067   $82.11   $82.10   $82.10  
  Purchase #4 $152.93   11.298%   $170.208   $170.21   $170.20   $170.20  
  Purchase #5 $207.31   3.640%   $214.8561   $214.86   $214.85   $214.90  
  Purchase #6 $49.98   9.648%   $54.8021   $54.80   $54.80   $54.80  
  Purchase #7 $226.53   10.792%   $250.9771   $250.98   $251.00   $251.00  
  7 purchase totals = $1,028.49       $1,115.2558   $1,115.27   $1,115.30   $1,115.30