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 $227.39   10.763%   $251.864   $251.86   $251.85   $251.90  
  Purchase #2 $107.74   10.304%   $118.8415   $118.84   $118.85   $118.80  
  Purchase #3 $43.71   7.361%   $46.9275   $46.93   $46.95   $46.90  
  Purchase #4 $172.41   12.751%   $194.394   $194.39   $194.40   $194.40  
  Purchase #5 $45.46   11.496%   $50.6861   $50.69   $50.70   $50.70  
  Purchase #6 $190.54   5.113%   $200.2823   $200.28   $200.30   $200.30  
  Purchase #7 $195.43   8.851%   $212.7275   $212.73   $212.75   $212.70  
  7 purchase totals = $982.68       $1,075.7229   $1,075.72   $1,075.80   $1,075.70