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 $54.40   11.449%   $60.6283   $60.63   $60.65   $60.60  
  Purchase #2 $177.61   9.384%   $194.2769   $194.28   $194.30   $194.30  
  Purchase #3 $203.65   6.598%   $217.0868   $217.09   $217.10   $217.10  
  Purchase #4 $227.54   12.603%   $256.2169   $256.22   $256.20   $256.20  
  Purchase #5 $190.51   7.387%   $204.583   $204.58   $204.60   $204.60  
  Purchase #6 $49.69   9.118%   $54.2207   $54.22   $54.20   $54.20  
  Purchase #7 $121.64   4.279%   $126.845   $126.85   $126.85   $126.80  
  7 purchase totals = $1,025.04       $1,113.8576   $1,113.87   $1,113.90   $1,113.80