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 $83.58   12.408%   $93.9506   $93.95   $93.95   $94.00  
  Purchase #2 $36.25   5.362%   $38.1937   $38.19   $38.20   $38.20  
  Purchase #3 $131.51   7.701%   $141.6376   $141.64   $141.65   $141.60  
  Purchase #4 $17.78   6.478%   $18.9318   $18.93   $18.95   $18.90  
  Purchase #5 $119.43   10.294%   $131.7241   $131.72   $131.70   $131.70  
  Purchase #6 $52.38   6.234%   $55.6454   $55.65   $55.65   $55.60  
  Purchase #7 $219.37   12.654%   $247.1291   $247.13   $247.15   $247.10  
  7 purchase totals = $660.30       $727.2123   $727.21   $727.25   $727.10