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 $84.92   11.829%   $94.9652   $94.97   $94.95   $95.00  
  Purchase #2 $80.94   11.129%   $89.9478   $89.95   $89.95   $89.90  
  Purchase #3 $43.75   8.523%   $47.4788   $47.48   $47.50   $47.50  
  Purchase #4 $160.45   3.651%   $166.308   $166.31   $166.30   $166.30  
  Purchase #5 $225.60   12.123%   $252.9495   $252.95   $252.95   $252.90  
  Purchase #6 $92.73   9.111%   $101.1786   $101.18   $101.20   $101.20  
  Purchase #7 $230.49   13.603%   $261.8436   $261.84   $261.85   $261.80  
  7 purchase totals = $918.88       $1,014.6715   $1,014.68   $1,014.70   $1,014.60