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 $217.79   8.241%   $235.7381   $235.74   $235.75   $235.70  
  Purchase #2 $166.61   10.414%   $183.9608   $183.96   $183.95   $184.00  
  Purchase #3 $167.36   10.343%   $184.67   $184.67   $184.65   $184.70  
  Purchase #4 $151.75   3.588%   $157.1948   $157.19   $157.20   $157.20  
  Purchase #5 $100.78   5.508%   $106.331   $106.33   $106.35   $106.30  
  Purchase #6 $65.92   6.402%   $70.1402   $70.14   $70.15   $70.10  
  Purchase #7 $189.88   9.857%   $208.5965   $208.60   $208.60   $208.60  
  7 purchase totals = $1,060.09       $1,146.6314   $1,146.63   $1,146.65   $1,146.60