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 $38.86   12.672%   $43.7843   $43.78   $43.80   $43.80  
  Purchase #2 $180.38   8.503%   $195.7177   $195.72   $195.70   $195.70  
  Purchase #3 $173.28   13.666%   $196.9604   $196.96   $196.95   $197.00  
  Purchase #4 $162.59   4.236%   $169.4773   $169.48   $169.50   $169.50  
  Purchase #5 $177.39   13.126%   $200.6742   $200.67   $200.65   $200.70  
  Purchase #6 $101.62   7.868%   $109.6155   $109.62   $109.60   $109.60  
  Purchase #7 $196.74   11.309%   $218.9893   $218.99   $219.00   $219.00  
  7 purchase totals = $1,030.86       $1,135.2187   $1,135.22   $1,135.20   $1,135.30