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 $84.34   12.841%   $95.1701   $95.17   $95.15   $95.20  
  Purchase #2 $222.61   13.294%   $252.2038   $252.20   $252.20   $252.20  
  Purchase #3 $153.51   5.548%   $162.0267   $162.03   $162.05   $162.00  
  Purchase #4 $20.67   3.213%   $21.3341   $21.33   $21.35   $21.30  
  Purchase #5 $205.69   3.160%   $212.1898   $212.19   $212.20   $212.20  
  Purchase #6 $127.39   4.152%   $132.6792   $132.68   $132.70   $132.70  
  Purchase #7 $67.45   11.335%   $75.0955   $75.10   $75.10   $75.10  
  7 purchase totals = $881.66       $950.6992   $950.70   $950.75   $950.70