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 $89.84   9.613%   $98.4763   $98.48   $98.50   $98.50  
  Purchase #2 $239.68   5.137%   $251.9924   $251.99   $252.00   $252.00  
  Purchase #3 $199.87   10.374%   $220.6045   $220.60   $220.60   $220.60  
  Purchase #4 $228.49   6.464%   $243.2596   $243.26   $243.25   $243.30  
  Purchase #5 $145.63   5.200%   $153.2028   $153.20   $153.20   $153.20  
  Purchase #6 $171.73   6.628%   $183.1123   $183.11   $183.10   $183.10  
  Purchase #7 $59.73   4.302%   $62.2996   $62.30   $62.30   $62.30  
  7 purchase totals = $1,134.97       $1,212.9475   $1,212.94   $1,212.95   $1,213.00