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 $214.74   5.719%   $227.021   $227.02   $227.00   $227.00  
  Purchase #2 $32.59   5.871%   $34.5034   $34.50   $34.50   $34.50  
  Purchase #3 $152.80   11.220%   $169.9442   $169.94   $169.95   $169.90  
  Purchase #4 $196.42   4.395%   $205.0527   $205.05   $205.05   $205.10  
  Purchase #5 $245.78   12.292%   $275.9913   $275.99   $276.00   $276.00  
  Purchase #6 $178.64   9.852%   $196.2396   $196.24   $196.25   $196.20  
  Purchase #7 $153.49   6.572%   $163.5774   $163.58   $163.60   $163.60  
  7 purchase totals = $1,174.46       $1,272.3296   $1,272.32   $1,272.35   $1,272.30