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 $207.66   11.847%   $232.2615   $232.26   $232.25   $232.30  
  Purchase #2 $174.27   5.645%   $184.1075   $184.11   $184.10   $184.10  
  Purchase #3 $146.33   4.785%   $153.3319   $153.33   $153.35   $153.30  
  Purchase #4 $148.74   8.527%   $161.4231   $161.42   $161.40   $161.40  
  Purchase #5 $83.43   4.108%   $86.8573   $86.86   $86.85   $86.90  
  Purchase #6 $115.46   10.428%   $127.5002   $127.50   $127.50   $127.50  
  Purchase #7 $105.97   10.197%   $116.7758   $116.78   $116.80   $116.80  
  7 purchase totals = $981.86       $1,062.2573   $1,062.26   $1,062.25   $1,062.30