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 $194.66   9.232%   $212.631   $212.63   $212.65   $212.60  
  Purchase #2 $124.51   4.451%   $130.0519   $130.05   $130.05   $130.10  
  Purchase #3 $110.31   6.186%   $117.1338   $117.13   $117.15   $117.10  
  Purchase #4 $243.41   7.782%   $262.3522   $262.35   $262.35   $262.40  
  Purchase #5 $220.95   10.758%   $244.7198   $244.72   $244.70   $244.70  
  Purchase #6 $151.94   12.811%   $171.405   $171.41   $171.40   $171.40  
  Purchase #7 $150.60   10.370%   $166.2172   $166.22   $166.20   $166.20  
  7 purchase totals = $1,196.38       $1,304.5109   $1,304.51   $1,304.50   $1,304.50