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 $53.95   10.340%   $59.5284   $59.53   $59.55   $59.50  
  Purchase #2 $142.65   4.779%   $149.4672   $149.47   $149.45   $149.50  
  Purchase #3 $245.69   8.828%   $267.3795   $267.38   $267.40   $267.40  
  Purchase #4 $166.77   10.465%   $184.2225   $184.22   $184.20   $184.20  
  Purchase #5 $200.53   9.861%   $220.3043   $220.30   $220.30   $220.30  
  Purchase #6 $58.50   13.764%   $66.5519   $66.55   $66.55   $66.60  
  Purchase #7 $160.77   11.136%   $178.6733   $178.67   $178.65   $178.70  
  7 purchase totals = $1,028.86       $1,126.1271   $1,126.12   $1,126.10   $1,126.20