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 $48.76   8.184%   $52.7505   $52.75   $52.75   $52.80  
  Purchase #2 $186.63   11.214%   $207.5587   $207.56   $207.55   $207.60  
  Purchase #3 $70.96   4.283%   $73.9992   $74.00   $74.00   $74.00  
  Purchase #4 $210.42   9.238%   $229.8586   $229.86   $229.85   $229.90  
  Purchase #5 $238.58   13.377%   $270.4948   $270.49   $270.50   $270.50  
  Purchase #6 $126.74   6.744%   $135.2873   $135.29   $135.30   $135.30  
  Purchase #7 $183.62   12.370%   $206.3338   $206.33   $206.35   $206.30  
  7 purchase totals = $1,065.71       $1,176.2829   $1,176.28   $1,176.30   $1,176.40