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 $115.93   3.208%   $119.649   $119.65   $119.65   $119.60  
  Purchase #2 $159.47   6.567%   $169.9424   $169.94   $169.95   $169.90  
  Purchase #3 $203.36   4.403%   $212.3139   $212.31   $212.30   $212.30  
  Purchase #4 $157.77   7.868%   $170.1833   $170.18   $170.20   $170.20  
  Purchase #5 $169.57   3.163%   $174.9335   $174.93   $174.95   $174.90  
  Purchase #6 $158.76   8.754%   $172.6579   $172.66   $172.65   $172.70  
  Purchase #7 $209.77   11.597%   $234.097   $234.10   $234.10   $234.10  
  7 purchase totals = $1,174.63       $1,253.7770   $1,253.77   $1,253.80   $1,253.70