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 $175.40   11.659%   $195.8499   $195.85   $195.85   $195.80  
  Purchase #2 $232.74   12.121%   $260.9504   $260.95   $260.95   $261.00  
  Purchase #3 $47.64   11.648%   $53.1891   $53.19   $53.20   $53.20  
  Purchase #4 $147.53   5.495%   $155.6368   $155.64   $155.65   $155.60  
  Purchase #5 $88.54   11.227%   $98.4804   $98.48   $98.50   $98.50  
  Purchase #6 $102.94   6.578%   $109.7114   $109.71   $109.70   $109.70  
  Purchase #7 $210.51   9.146%   $229.7632   $229.76   $229.75   $229.80  
  7 purchase totals = $1,005.30       $1,103.5812   $1,103.58   $1,103.60   $1,103.60