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 $222.58   4.692%   $233.0235   $233.02   $233.00   $233.00  
  Purchase #2 $113.59   4.190%   $118.3494   $118.35   $118.35   $118.30  
  Purchase #3 $23.48   13.830%   $26.7273   $26.73   $26.75   $26.70  
  Purchase #4 $110.60   5.649%   $116.8478   $116.85   $116.85   $116.80  
  Purchase #5 $127.63   11.319%   $142.0764   $142.08   $142.10   $142.10  
  Purchase #6 $187.99   5.184%   $197.7354   $197.74   $197.75   $197.70  
  Purchase #7 $109.85   8.852%   $119.5739   $119.57   $119.55   $119.60  
  7 purchase totals = $895.72       $954.3337   $954.34   $954.35   $954.20