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 $90.59   5.604%   $95.6667   $95.67   $95.65   $95.70  
  Purchase #2 $156.93   13.636%   $178.329   $178.33   $178.35   $178.30  
  Purchase #3 $166.65   11.120%   $185.1815   $185.18   $185.20   $185.20  
  Purchase #4 $246.65   5.843%   $261.0618   $261.06   $261.05   $261.10  
  Purchase #5 $86.70   12.117%   $97.2054   $97.21   $97.20   $97.20  
  Purchase #6 $38.31   4.188%   $39.9144   $39.91   $39.90   $39.90  
  Purchase #7 $176.27   8.597%   $191.4239   $191.42   $191.40   $191.40  
  7 purchase totals = $962.10       $1,048.7827   $1,048.78   $1,048.75   $1,048.80