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 $88.30   6.612%   $94.1384   $94.14   $94.15   $94.10  
  Purchase #2 $214.65   13.707%   $244.0721   $244.07   $244.05   $244.10  
  Purchase #3 $50.85   3.557%   $52.6587   $52.66   $52.65   $52.70  
  Purchase #4 $244.54   6.689%   $260.8973   $260.90   $260.90   $260.90  
  Purchase #5 $171.41   10.383%   $189.2075   $189.21   $189.20   $189.20  
  Purchase #6 $100.58   13.303%   $113.9602   $113.96   $113.95   $114.00  
  Purchase #7 $206.44   7.750%   $222.4391   $222.44   $222.45   $222.40  
  7 purchase totals = $1,076.77       $1,177.3733   $1,177.38   $1,177.35   $1,177.40