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 $218.96   5.328%   $230.6262   $230.63   $230.65   $230.60  
  Purchase #2 $47.95   4.803%   $50.253   $50.25   $50.25   $50.30  
  Purchase #3 $93.92   12.468%   $105.6299   $105.63   $105.65   $105.60  
  Purchase #4 $233.36   10.369%   $257.5571   $257.56   $257.55   $257.60  
  Purchase #5 $156.69   8.113%   $169.4023   $169.40   $169.40   $169.40  
  Purchase #6 $191.47   5.412%   $201.8324   $201.83   $201.85   $201.80  
  Purchase #7 $194.67   12.687%   $219.3678   $219.37   $219.35   $219.40  
  7 purchase totals = $1,137.02       $1,234.6687   $1,234.67   $1,234.70   $1,234.70