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 $67.60   10.433%   $74.6527   $74.65   $74.65   $74.70  
  Purchase #2 $123.78   10.242%   $136.4575   $136.46   $136.45   $136.50  
  Purchase #3 $115.40   9.426%   $126.2776   $126.28   $126.30   $126.30  
  Purchase #4 $249.92   8.417%   $270.9558   $270.96   $270.95   $271.00  
  Purchase #5 $7.95   7.315%   $8.5315   $8.53   $8.55   $8.50  
  Purchase #6 $200.49   10.569%   $221.6798   $221.68   $221.70   $221.70  
  Purchase #7 $160.40   8.444%   $173.9442   $173.94   $173.95   $173.90  
  7 purchase totals = $925.54       $1,012.4991   $1,012.50   $1,012.55   $1,012.60