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 $199.69   7.585%   $214.8365   $214.84   $214.85   $214.80  
  Purchase #2 $90.26   6.537%   $96.1603   $96.16   $96.15   $96.20  
  Purchase #3 $196.93   9.137%   $214.9235   $214.92   $214.90   $214.90  
  Purchase #4 $201.76   9.197%   $220.3159   $220.32   $220.30   $220.30  
  Purchase #5 $68.45   13.432%   $77.6442   $77.64   $77.65   $77.60  
  Purchase #6 $219.87   11.284%   $244.6801   $244.68   $244.70   $244.70  
  Purchase #7 $60.45   7.420%   $64.9354   $64.94   $64.95   $64.90  
  7 purchase totals = $1,037.41       $1,133.4959   $1,133.50   $1,133.50   $1,133.40