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 $88.53   6.160%   $93.9834   $93.98   $94.00   $94.00  
  Purchase #2 $22.49   6.499%   $23.9516   $23.95   $23.95   $24.00  
  Purchase #3 $113.60   12.618%   $127.934   $127.93   $127.95   $127.90  
  Purchase #4 $221.42   8.803%   $240.9116   $240.91   $240.90   $240.90  
  Purchase #5 $202.64   4.102%   $210.9523   $210.95   $210.95   $211.00  
  Purchase #6 $227.94   3.673%   $236.3122   $236.31   $236.30   $236.30  
  Purchase #7 $221.95   5.764%   $234.7432   $234.74   $234.75   $234.70  
  7 purchase totals = $1,098.57       $1,168.7883   $1,168.77   $1,168.80   $1,168.80