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 $153.64   10.339%   $169.5248   $169.52   $169.50   $169.50  
  Purchase #2 $232.66   5.512%   $245.4842   $245.48   $245.50   $245.50  
  Purchase #3 $23.26   11.720%   $25.9861   $25.99   $26.00   $26.00  
  Purchase #4 $207.69   7.216%   $222.6769   $222.68   $222.70   $222.70  
  Purchase #5 $178.52   9.644%   $195.7365   $195.74   $195.75   $195.70  
  Purchase #6 $214.53   8.606%   $232.9925   $232.99   $233.00   $233.00  
  Purchase #7 $109.93   6.285%   $116.8391   $116.84   $116.85   $116.80  
  7 purchase totals = $1,120.23       $1,209.2401   $1,209.24   $1,209.30   $1,209.20