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 $62.98   12.326%   $70.7429   $70.74   $70.75   $70.70  
  Purchase #2 $163.64   9.477%   $179.1482   $179.15   $179.15   $179.10  
  Purchase #3 $124.30   7.175%   $133.2185   $133.22   $133.20   $133.20  
  Purchase #4 $185.76   9.634%   $203.6561   $203.66   $203.65   $203.70  
  Purchase #5 $33.61   5.409%   $35.428   $35.43   $35.45   $35.40  
  Purchase #6 $225.67   11.274%   $251.112   $251.11   $251.10   $251.10  
  Purchase #7 $85.84   7.249%   $92.0625   $92.06   $92.05   $92.10  
  7 purchase totals = $881.80       $965.3682   $965.37   $965.35   $965.30