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 $124.75   5.864%   $132.0653   $132.07   $132.05   $132.10  
  Purchase #2 $219.84   12.708%   $247.7773   $247.78   $247.80   $247.80  
  Purchase #3 $44.48   10.717%   $49.2469   $49.25   $49.25   $49.20  
  Purchase #4 $148.89   8.348%   $161.3193   $161.32   $161.30   $161.30  
  Purchase #5 $226.74   13.639%   $257.6651   $257.67   $257.65   $257.70  
  Purchase #6 $50.67   12.590%   $57.0494   $57.05   $57.05   $57.00  
  Purchase #7 $140.42   6.658%   $149.7692   $149.77   $149.75   $149.80  
  7 purchase totals = $955.79       $1,054.8925   $1,054.91   $1,054.85   $1,054.90