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 $174.87   8.823%   $190.2988   $190.30   $190.30   $190.30  
  Purchase #2 $221.73   10.347%   $244.6724   $244.67   $244.65   $244.70  
  Purchase #3 $101.37   4.260%   $105.6884   $105.69   $105.70   $105.70  
  Purchase #4 $25.63   13.367%   $29.056   $29.06   $29.05   $29.10  
  Purchase #5 $244.34   10.239%   $269.358   $269.36   $269.35   $269.40  
  Purchase #6 $186.51   7.425%   $200.3584   $200.36   $200.35   $200.40  
  Purchase #7 $60.93   7.203%   $65.3188   $65.32   $65.30   $65.30  
  7 purchase totals = $1,015.38       $1,104.7508   $1,104.76   $1,104.70   $1,104.90