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 $88.96   5.252%   $93.6322   $93.63   $93.65   $93.60  
  Purchase #2 $206.51   12.187%   $231.6774   $231.68   $231.70   $231.70  
  Purchase #3 $208.50   8.465%   $226.1495   $226.15   $226.15   $226.10  
  Purchase #4 $241.29   9.315%   $263.7662   $263.77   $263.75   $263.80  
  Purchase #5 $188.84   11.527%   $210.6076   $210.61   $210.60   $210.60  
  Purchase #6 $18.54   12.165%   $20.7954   $20.80   $20.80   $20.80  
  Purchase #7 $96.34   8.347%   $104.3815   $104.38   $104.40   $104.40  
  7 purchase totals = $1,048.98       $1,151.0098   $1,151.02   $1,151.05   $1,151.00