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 $141.31   7.536%   $151.9591   $151.96   $151.95   $152.00  
  Purchase #2 $218.53   12.857%   $246.6264   $246.63   $246.65   $246.60  
  Purchase #3 $94.90   11.649%   $105.9549   $105.95   $105.95   $106.00  
  Purchase #4 $224.66   3.603%   $232.7545   $232.75   $232.75   $232.80  
  Purchase #5 $130.55   5.615%   $137.8804   $137.88   $137.90   $137.90  
  Purchase #6 $14.49   13.466%   $16.4412   $16.44   $16.45   $16.40  
  Purchase #7 $199.96   9.475%   $218.9062   $218.91   $218.90   $218.90  
  7 purchase totals = $1,024.40       $1,110.5227   $1,110.52   $1,110.55   $1,110.60