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 $114.66   3.127%   $118.2454   $118.25   $118.25   $118.20  
  Purchase #2 $183.28   7.580%   $197.1726   $197.17   $197.15   $197.20  
  Purchase #3 $148.49   9.221%   $162.1823   $162.18   $162.20   $162.20  
  Purchase #4 $50.79   8.171%   $54.9401   $54.94   $54.95   $54.90  
  Purchase #5 $157.64   10.504%   $174.1985   $174.20   $174.20   $174.20  
  Purchase #6 $111.58   12.118%   $125.1013   $125.10   $125.10   $125.10  
  Purchase #7 $170.87   11.663%   $190.7986   $190.80   $190.80   $190.80  
  7 purchase totals = $937.31       $1,022.6388   $1,022.64   $1,022.65   $1,022.60