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 $195.87   11.160%   $217.7291   $217.73   $217.75   $217.70  
  Purchase #2 $47.84   10.798%   $53.0058   $53.01   $53.00   $53.00  
  Purchase #3 $155.36   10.567%   $171.7769   $171.78   $171.80   $171.80  
  Purchase #4 $118.83   5.670%   $125.5677   $125.57   $125.55   $125.60  
  Purchase #5 $119.90   6.592%   $127.8038   $127.80   $127.80   $127.80  
  Purchase #6 $188.56   8.842%   $205.2325   $205.23   $205.25   $205.20  
  Purchase #7 $158.86   5.257%   $167.2113   $167.21   $167.20   $167.20  
  7 purchase totals = $985.22       $1,068.3271   $1,068.33   $1,068.35   $1,068.30