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 $216.91   7.403%   $232.9678   $232.97   $232.95   $233.00  
  Purchase #2 $80.98   11.523%   $90.3113   $90.31   $90.30   $90.30  
  Purchase #3 $196.37   12.837%   $221.578   $221.58   $221.60   $221.60  
  Purchase #4 $227.28   12.373%   $255.4014   $255.40   $255.40   $255.40  
  Purchase #5 $24.71   5.551%   $26.0817   $26.08   $26.10   $26.10  
  Purchase #6 $141.43   5.288%   $148.9088   $148.91   $148.90   $148.90  
  Purchase #7 $157.31   7.529%   $169.1539   $169.15   $169.15   $169.20  
  7 purchase totals = $1,044.99       $1,144.4029   $1,144.40   $1,144.40   $1,144.50