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 $86.29   10.713%   $95.5342   $95.53   $95.55   $95.50  
  Purchase #2 $87.59   5.301%   $92.2331   $92.23   $92.25   $92.20  
  Purchase #3 $11.52   11.563%   $12.8521   $12.85   $12.85   $12.90  
  Purchase #4 $246.86   12.499%   $277.715   $277.72   $277.70   $277.70  
  Purchase #5 $213.87   6.435%   $227.6325   $227.63   $227.65   $227.60  
  Purchase #6 $192.86   6.250%   $204.9138   $204.91   $204.90   $204.90  
  Purchase #7 $124.95   13.163%   $141.3972   $141.40   $141.40   $141.40  
  7 purchase totals = $963.94       $1,052.2779   $1,052.27   $1,052.30   $1,052.20