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 $40.41   11.194%   $44.9335   $44.93   $44.95   $44.90  
  Purchase #2 $208.87   11.431%   $232.7459   $232.75   $232.75   $232.70  
  Purchase #3 $171.86   13.582%   $195.202   $195.20   $195.20   $195.20  
  Purchase #4 $211.64   10.714%   $234.3151   $234.32   $234.30   $234.30  
  Purchase #5 $230.81   5.737%   $244.0516   $244.05   $244.05   $244.10  
  Purchase #6 $87.47   12.183%   $98.1265   $98.13   $98.15   $98.10  
  Purchase #7 $40.97   9.206%   $44.7417   $44.74   $44.75   $44.70  
  7 purchase totals = $992.03       $1,094.1163   $1,094.12   $1,094.15   $1,094.00