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 $219.75   6.268%   $233.5239   $233.52   $233.50   $233.50  
  Purchase #2 $12.69   8.472%   $13.7651   $13.77   $13.75   $13.80  
  Purchase #3 $219.60   3.613%   $227.5341   $227.53   $227.55   $227.50  
  Purchase #4 $45.67   9.600%   $50.0543   $50.05   $50.05   $50.10  
  Purchase #5 $170.65   13.864%   $194.3089   $194.31   $194.30   $194.30  
  Purchase #6 $118.95   4.764%   $124.6168   $124.62   $124.60   $124.60  
  Purchase #7 $244.90   11.362%   $272.7255   $272.73   $272.75   $272.70  
  7 purchase totals = $1,032.21       $1,116.5286   $1,116.53   $1,116.50   $1,116.50