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 $86.70   8.658%   $94.2065   $94.21   $94.20   $94.20  
  Purchase #2 $160.99   9.411%   $176.1408   $176.14   $176.15   $176.10  
  Purchase #3 $206.27   10.513%   $227.9552   $227.96   $227.95   $228.00  
  Purchase #4 $208.73   3.677%   $216.405   $216.41   $216.40   $216.40  
  Purchase #5 $200.98   12.707%   $226.5185   $226.52   $226.50   $226.50  
  Purchase #6 $24.95   3.849%   $25.9103   $25.91   $25.90   $25.90  
  Purchase #7 $174.77   9.765%   $191.8363   $191.84   $191.85   $191.80  
  7 purchase totals = $1,063.39       $1,158.9726   $1,158.99   $1,158.95   $1,158.90