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 $232.27   5.121%   $244.1645   $244.16   $244.15   $244.20  
  Purchase #2 $46.29   11.598%   $51.6587   $51.66   $51.65   $51.70  
  Purchase #3 $194.32   5.485%   $204.9785   $204.98   $205.00   $205.00  
  Purchase #4 $228.85   3.584%   $237.052   $237.05   $237.05   $237.10  
  Purchase #5 $54.36   8.708%   $59.0937   $59.09   $59.10   $59.10  
  Purchase #6 $63.28   6.239%   $67.228   $67.23   $67.25   $67.20  
  Purchase #7 $145.72   8.722%   $158.4297   $158.43   $158.45   $158.40  
  7 purchase totals = $965.09       $1,022.6051   $1,022.60   $1,022.65   $1,022.70