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 $59.41   4.413%   $62.0318   $62.03   $62.05   $62.00  
  Purchase #2 $200.25   7.168%   $214.6039   $214.60   $214.60   $214.60  
  Purchase #3 $28.58   4.406%   $29.8392   $29.84   $29.85   $29.80  
  Purchase #4 $217.65   9.442%   $238.2005   $238.20   $238.20   $238.20  
  Purchase #5 $68.31   7.499%   $73.4326   $73.43   $73.45   $73.40  
  Purchase #6 $61.49   7.439%   $66.0642   $66.06   $66.05   $66.10  
  Purchase #7 $86.36   4.531%   $90.273   $90.27   $90.25   $90.30  
  7 purchase totals = $722.05       $774.4452   $774.43   $774.45   $774.40