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 $71.99   5.191%   $75.727   $75.73   $75.75   $75.70  
  Purchase #2 $217.42   12.698%   $245.028   $245.03   $245.05   $245.00  
  Purchase #3 $226.79   6.551%   $241.647   $241.65   $241.65   $241.60  
  Purchase #4 $64.36   10.824%   $71.3263   $71.33   $71.35   $71.30  
  Purchase #5 $246.72   10.292%   $272.1124   $272.11   $272.10   $272.10  
  Purchase #6 $201.98   7.734%   $217.6011   $217.60   $217.60   $217.60  
  Purchase #7 $166.30   10.351%   $183.5137   $183.51   $183.50   $183.50  
  7 purchase totals = $1,195.56       $1,306.9555   $1,306.96   $1,307.00   $1,306.80