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 $202.50   5.699%   $214.0405   $214.04   $214.05   $214.00  
  Purchase #2 $62.99   4.186%   $65.6268   $65.63   $65.65   $65.60  
  Purchase #3 $137.77   12.195%   $154.5711   $154.57   $154.55   $154.60  
  Purchase #4 $60.70   12.241%   $68.1303   $68.13   $68.15   $68.10  
  Purchase #5 $107.97   11.464%   $120.3477   $120.35   $120.35   $120.30  
  Purchase #6 $173.78   12.200%   $194.9812   $194.98   $195.00   $195.00  
  Purchase #7 $184.76   3.430%   $191.0973   $191.10   $191.10   $191.10  
  7 purchase totals = $930.47       $1,008.7949   $1,008.80   $1,008.85   $1,008.70