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 $196.46   4.784%   $205.8586   $205.86   $205.85   $205.90  
  Purchase #2 $68.26   10.756%   $75.602   $75.60   $75.60   $75.60  
  Purchase #3 $216.27   10.184%   $238.2949   $238.29   $238.30   $238.30  
  Purchase #4 $60.36   3.424%   $62.4267   $62.43   $62.45   $62.40  
  Purchase #5 $70.32   6.569%   $74.9393   $74.94   $74.95   $74.90  
  Purchase #6 $195.27   10.111%   $215.0137   $215.01   $215.00   $215.00  
  Purchase #7 $219.94   3.191%   $226.9583   $226.96   $226.95   $227.00  
  7 purchase totals = $1,026.88       $1,099.0935   $1,099.09   $1,099.10   $1,099.10