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 $116.98   8.551%   $126.983   $126.98   $127.00   $127.00  
  Purchase #2 $136.25   9.653%   $149.4022   $149.40   $149.40   $149.40  
  Purchase #3 $23.44   6.120%   $24.8745   $24.87   $24.85   $24.90  
  Purchase #4 $114.40   12.557%   $128.7652   $128.77   $128.75   $128.80  
  Purchase #5 $244.95   5.737%   $259.0028   $259.00   $259.00   $259.00  
  Purchase #6 $185.53   6.462%   $197.5189   $197.52   $197.50   $197.50  
  Purchase #7 $125.95   8.213%   $136.2943   $136.29   $136.30   $136.30  
  7 purchase totals = $947.50       $1,022.8409   $1,022.83   $1,022.80   $1,022.90