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 $63.92   13.602%   $72.6144   $72.61   $72.60   $72.60  
  Purchase #2 $233.43   5.449%   $246.1496   $246.15   $246.15   $246.10  
  Purchase #3 $150.90   13.165%   $170.766   $170.77   $170.75   $170.80  
  Purchase #4 $236.73   3.426%   $244.8404   $244.84   $244.85   $244.80  
  Purchase #5 $196.79   3.488%   $203.654   $203.65   $203.65   $203.70  
  Purchase #6 $168.32   5.611%   $177.7644   $177.76   $177.75   $177.80  
  Purchase #7 $73.38   7.369%   $78.7874   $78.79   $78.80   $78.80  
  7 purchase totals = $1,123.47       $1,194.5762   $1,194.57   $1,194.55   $1,194.60