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 $86.28   11.219%   $95.9598   $95.96   $95.95   $96.00  
  Purchase #2 $220.32   8.463%   $238.9657   $238.97   $238.95   $239.00  
  Purchase #3 $239.61   10.740%   $265.3441   $265.34   $265.35   $265.30  
  Purchase #4 $141.43   9.546%   $154.9309   $154.93   $154.95   $154.90  
  Purchase #5 $233.29   6.261%   $247.8963   $247.90   $247.90   $247.90  
  Purchase #6 $181.43   4.648%   $189.8629   $189.86   $189.85   $189.90  
  Purchase #7 $243.36   3.476%   $251.8192   $251.82   $251.80   $251.80  
  7 purchase totals = $1,345.72       $1,444.7789   $1,444.78   $1,444.75   $1,444.80