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 $180.80   8.331%   $195.8624   $195.86   $195.85   $195.90  
  Purchase #2 $248.84   4.733%   $260.6176   $260.62   $260.60   $260.60  
  Purchase #3 $167.62   13.499%   $190.247   $190.25   $190.25   $190.20  
  Purchase #4 $110.46   6.195%   $117.303   $117.30   $117.30   $117.30  
  Purchase #5 $124.63   11.829%   $139.3725   $139.37   $139.35   $139.40  
  Purchase #6 $207.87   6.465%   $221.3088   $221.31   $221.30   $221.30  
  Purchase #7 $48.64   6.511%   $51.807   $51.81   $51.80   $51.80  
  7 purchase totals = $1,088.86       $1,176.5183   $1,176.52   $1,176.45   $1,176.50