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 $215.86   13.324%   $244.6212   $244.62   $244.60   $244.60  
  Purchase #2 $205.86   7.158%   $220.5955   $220.60   $220.60   $220.60  
  Purchase #3 $162.89   4.736%   $170.6045   $170.60   $170.60   $170.60  
  Purchase #4 $36.99   4.328%   $38.5909   $38.59   $38.60   $38.60  
  Purchase #5 $32.38   6.160%   $34.3746   $34.37   $34.35   $34.40  
  Purchase #6 $119.49   10.436%   $131.96   $131.96   $131.95   $132.00  
  Purchase #7 $152.63   4.643%   $159.7166   $159.72   $159.70   $159.70  
  7 purchase totals = $926.10       $1,000.4633   $1,000.46   $1,000.40   $1,000.50