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 $191.75   11.625%   $214.0409   $214.04   $214.05   $214.00  
  Purchase #2 $87.67   10.126%   $96.5475   $96.55   $96.55   $96.50  
  Purchase #3 $201.89   10.872%   $223.8395   $223.84   $223.85   $223.80  
  Purchase #4 $115.99   5.239%   $122.0667   $122.07   $122.05   $122.10  
  Purchase #5 $101.96   8.476%   $110.6021   $110.60   $110.60   $110.60  
  Purchase #6 $45.62   13.358%   $51.7139   $51.71   $51.70   $51.70  
  Purchase #7 $103.31   10.472%   $114.1286   $114.13   $114.15   $114.10  
  7 purchase totals = $848.19       $932.9392   $932.94   $932.95   $932.80