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 $95.68   10.370%   $105.602   $105.60   $105.60   $105.60  
  Purchase #2 $64.45   12.644%   $72.5991   $72.60   $72.60   $72.60  
  Purchase #3 $12.52   11.451%   $13.9537   $13.95   $13.95   $14.00  
  Purchase #4 $205.29   12.251%   $230.4401   $230.44   $230.45   $230.40  
  Purchase #5 $248.53   13.744%   $282.688   $282.69   $282.70   $282.70  
  Purchase #6 $158.45   4.120%   $164.9781   $164.98   $165.00   $165.00  
  Purchase #7 $37.72   5.510%   $39.7984   $39.80   $39.80   $39.80  
  7 purchase totals = $822.64       $910.0594   $910.06   $910.10   $910.10