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 $195.89   5.148%   $205.9744   $205.97   $205.95   $206.00  
  Purchase #2 $54.98   3.502%   $56.9054   $56.91   $56.90   $56.90  
  Purchase #3 $211.34   3.395%   $218.515   $218.52   $218.50   $218.50  
  Purchase #4 $194.99   11.663%   $217.7317   $217.73   $217.75   $217.70  
  Purchase #5 $125.30   9.502%   $137.206   $137.21   $137.20   $137.20  
  Purchase #6 $106.81   13.737%   $121.4825   $121.48   $121.50   $121.50  
  Purchase #7 $244.33   13.391%   $277.0482   $277.05   $277.05   $277.00  
  7 purchase totals = $1,133.64       $1,234.8632   $1,234.87   $1,234.85   $1,234.80