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 $55.48   10.804%   $61.4741   $61.47   $61.45   $61.50  
  Purchase #2 $194.49   4.253%   $202.7617   $202.76   $202.75   $202.80  
  Purchase #3 $238.78   12.490%   $268.6036   $268.60   $268.60   $268.60  
  Purchase #4 $213.49   3.842%   $221.6923   $221.69   $221.70   $221.70  
  Purchase #5 $72.95   5.466%   $76.9374   $76.94   $76.95   $76.90  
  Purchase #6 $127.92   4.496%   $133.6713   $133.67   $133.65   $133.70  
  Purchase #7 $143.73   4.340%   $149.9679   $149.97   $149.95   $150.00  
  7 purchase totals = $1,046.84       $1,115.1083   $1,115.10   $1,115.05   $1,115.20