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 $85.93   10.163%   $94.6631   $94.66   $94.65   $94.70  
  Purchase #2 $189.53   7.193%   $203.1629   $203.16   $203.15   $203.20  
  Purchase #3 $33.82   6.247%   $35.9327   $35.93   $35.95   $35.90  
  Purchase #4 $226.51   4.610%   $236.9521   $236.95   $236.95   $237.00  
  Purchase #5 $221.69   10.776%   $245.5793   $245.58   $245.60   $245.60  
  Purchase #6 $196.27   3.404%   $202.951   $202.95   $202.95   $203.00  
  Purchase #7 $48.53   13.413%   $55.0393   $55.04   $55.05   $55.00  
  7 purchase totals = $1,002.28       $1,074.2804   $1,074.27   $1,074.30   $1,074.40