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 $32.61   5.630%   $34.4459   $34.45   $34.45   $34.40  
  Purchase #2 $37.94   3.802%   $39.3825   $39.38   $39.40   $39.40  
  Purchase #3 $92.70   4.170%   $96.5656   $96.57   $96.55   $96.60  
  Purchase #4 $107.41   11.262%   $119.5065   $119.51   $119.50   $119.50  
  Purchase #5 $160.33   6.526%   $170.7931   $170.79   $170.80   $170.80  
  Purchase #6 $102.97   3.590%   $106.6666   $106.67   $106.65   $106.70  
  Purchase #7 $127.91   3.671%   $132.6056   $132.61   $132.60   $132.60  
  7 purchase totals = $661.87       $699.9658   $699.98   $699.95   $700.00