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 $58.76   6.467%   $62.56   $62.56   $62.55   $62.60  
  Purchase #2 $158.33   7.394%   $170.0369   $170.04   $170.05   $170.00  
  Purchase #3 $52.61   9.567%   $57.6432   $57.64   $57.65   $57.60  
  Purchase #4 $5.64   11.712%   $6.3006   $6.30   $6.30   $6.30  
  Purchase #5 $202.78   6.695%   $216.3561   $216.36   $216.35   $216.40  
  Purchase #6 $51.83   6.306%   $55.0984   $55.10   $55.10   $55.10  
  Purchase #7 $175.80   10.699%   $194.6088   $194.61   $194.60   $194.60  
  7 purchase totals = $705.75       $762.6040   $762.61   $762.60   $762.60