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 $186.82   4.375%   $194.9934   $194.99   $195.00   $195.00  
  Purchase #2 $244.38   9.593%   $267.8234   $267.82   $267.80   $267.80  
  Purchase #3 $220.95   4.870%   $231.7103   $231.71   $231.70   $231.70  
  Purchase #4 $233.34   7.313%   $250.4042   $250.40   $250.40   $250.40  
  Purchase #5 $48.55   3.235%   $50.1206   $50.12   $50.10   $50.10  
  Purchase #6 $40.94   5.831%   $43.3272   $43.33   $43.35   $43.30  
  Purchase #7 $148.91   5.196%   $156.6474   $156.65   $156.65   $156.60  
  7 purchase totals = $1,123.89       $1,195.0265   $1,195.02   $1,195.00   $1,194.90