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 $210.74   10.402%   $232.6612   $232.66   $232.65   $232.70  
  Purchase #2 $87.97   9.534%   $96.3571   $96.36   $96.35   $96.40  
  Purchase #3 $66.37   7.442%   $71.3093   $71.31   $71.30   $71.30  
  Purchase #4 $58.92   11.519%   $65.707   $65.71   $65.70   $65.70  
  Purchase #5 $237.50   12.677%   $267.6079   $267.61   $267.60   $267.60  
  Purchase #6 $185.57   3.571%   $192.1967   $192.20   $192.20   $192.20  
  Purchase #7 $166.74   5.607%   $176.0891   $176.09   $176.10   $176.10  
  7 purchase totals = $1,013.81       $1,101.9283   $1,101.94   $1,101.90   $1,102.00