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 $162.41   4.417%   $169.5836   $169.58   $169.60   $169.60  
  Purchase #2 $177.47   11.452%   $197.7939   $197.79   $197.80   $197.80  
  Purchase #3 $130.25   10.317%   $143.6879   $143.69   $143.70   $143.70  
  Purchase #4 $223.81   9.355%   $244.7474   $244.75   $244.75   $244.70  
  Purchase #5 $246.92   11.687%   $275.7775   $275.78   $275.80   $275.80  
  Purchase #6 $221.30   13.507%   $251.191   $251.19   $251.20   $251.20  
  Purchase #7 $120.82   8.725%   $131.3615   $131.36   $131.35   $131.40  
  7 purchase totals = $1,282.98       $1,414.1428   $1,414.14   $1,414.20   $1,414.20