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 $61.76   12.864%   $69.7048   $69.70   $69.70   $69.70  
  Purchase #2 $10.45   11.769%   $11.6799   $11.68   $11.70   $11.70  
  Purchase #3 $96.37   5.608%   $101.7744   $101.77   $101.75   $101.80  
  Purchase #4 $198.76   9.855%   $218.3478   $218.35   $218.35   $218.30  
  Purchase #5 $232.34   6.482%   $247.4003   $247.40   $247.40   $247.40  
  Purchase #6 $17.42   5.377%   $18.3567   $18.36   $18.35   $18.40  
  Purchase #7 $195.63   7.444%   $210.1927   $210.19   $210.20   $210.20  
  7 purchase totals = $812.73       $877.4566   $877.45   $877.45   $877.50