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 $72.55   3.832%   $75.3301   $75.33   $75.35   $75.30  
  Purchase #2 $202.49   10.532%   $223.8162   $223.82   $223.80   $223.80  
  Purchase #3 $163.65   5.810%   $173.1581   $173.16   $173.15   $173.20  
  Purchase #4 $48.56   9.442%   $53.145   $53.15   $53.15   $53.10  
  Purchase #5 $124.93   3.491%   $129.2913   $129.29   $129.30   $129.30  
  Purchase #6 $232.66   4.430%   $242.9668   $242.97   $242.95   $243.00  
  Purchase #7 $124.55   10.428%   $137.5381   $137.54   $137.55   $137.50  
  7 purchase totals = $969.39       $1,035.2456   $1,035.26   $1,035.25   $1,035.20