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 $88.69   7.107%   $94.9932   $94.99   $95.00   $95.00  
  Purchase #2 $133.35   7.823%   $143.782   $143.78   $143.80   $143.80  
  Purchase #3 $9.75   3.512%   $10.0924   $10.09   $10.10   $10.10  
  Purchase #4 $119.79   11.425%   $133.476   $133.48   $133.50   $133.50  
  Purchase #5 $32.75   12.770%   $36.9322   $36.93   $36.95   $36.90  
  Purchase #6 $215.55   4.518%   $225.2885   $225.29   $225.30   $225.30  
  Purchase #7 $130.66   9.222%   $142.7095   $142.71   $142.70   $142.70  
  7 purchase totals = $730.54       $787.2738   $787.27   $787.35   $787.30