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 $209.83   7.320%   $225.1896   $225.19   $225.20   $225.20  
  Purchase #2 $235.96   4.170%   $245.7995   $245.80   $245.80   $245.80  
  Purchase #3 $227.45   9.539%   $249.1465   $249.15   $249.15   $249.10  
  Purchase #4 $148.26   12.814%   $167.258   $167.26   $167.25   $167.30  
  Purchase #5 $163.93   11.537%   $182.8426   $182.84   $182.85   $182.80  
  Purchase #6 $147.75   13.606%   $167.8529   $167.85   $167.85   $167.90  
  Purchase #7 $16.92   10.142%   $18.636   $18.64   $18.65   $18.60  
  7 purchase totals = $1,150.10       $1,256.7251   $1,256.73   $1,256.75   $1,256.70