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 $87.66   9.538%   $96.021   $96.02   $96.00   $96.00  
  Purchase #2 $227.82   5.580%   $240.5324   $240.53   $240.55   $240.50  
  Purchase #3 $56.78   13.857%   $64.648   $64.65   $64.65   $64.60  
  Purchase #4 $209.43   12.293%   $235.1752   $235.18   $235.20   $235.20  
  Purchase #5 $108.27   9.297%   $118.3359   $118.34   $118.35   $118.30  
  Purchase #6 $212.64   5.488%   $224.3097   $224.31   $224.30   $224.30  
  Purchase #7 $248.61   11.452%   $277.0808   $277.08   $277.10   $277.10  
  7 purchase totals = $1,151.21       $1,256.1030   $1,256.11   $1,256.15   $1,256.00