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 $216.99   7.606%   $233.4943   $233.49   $233.50   $233.50  
  Purchase #2 $46.93   4.837%   $49.2   $49.20   $49.20   $49.20  
  Purchase #3 $170.61   6.337%   $181.4216   $181.42   $181.40   $181.40  
  Purchase #4 $143.61   4.594%   $150.2074   $150.21   $150.20   $150.20  
  Purchase #5 $226.39   8.117%   $244.7661   $244.77   $244.75   $244.80  
  Purchase #6 $63.98   3.141%   $65.9896   $65.99   $66.00   $66.00  
  Purchase #7 $207.54   13.304%   $235.1511   $235.15   $235.15   $235.20  
  7 purchase totals = $1,076.05       $1,160.2301   $1,160.23   $1,160.20   $1,160.30