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 $65.86   3.408%   $68.1045   $68.10   $68.10   $68.10  
  Purchase #2 $190.66   4.868%   $199.9413   $199.94   $199.95   $199.90  
  Purchase #3 $148.70   12.476%   $167.2518   $167.25   $167.25   $167.30  
  Purchase #4 $5.75   6.228%   $6.1081   $6.11   $6.10   $6.10  
  Purchase #5 $175.49   13.702%   $199.5356   $199.54   $199.55   $199.50  
  Purchase #6 $195.55   11.461%   $217.962   $217.96   $217.95   $218.00  
  Purchase #7 $170.60   3.479%   $176.5352   $176.54   $176.55   $176.50  
  7 purchase totals = $952.61       $1,035.4385   $1,035.44   $1,035.45   $1,035.40