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 $88.54   5.776%   $93.6541   $93.65   $93.65   $93.70  
  Purchase #2 $125.41   3.856%   $130.2458   $130.25   $130.25   $130.20  
  Purchase #3 $100.47   7.485%   $107.9902   $107.99   $108.00   $108.00  
  Purchase #4 $106.58   10.124%   $117.3702   $117.37   $117.35   $117.40  
  Purchase #5 $213.43   13.826%   $242.9388   $242.94   $242.95   $242.90  
  Purchase #6 $174.84   7.355%   $187.6995   $187.70   $187.70   $187.70  
  Purchase #7 $167.26   4.457%   $174.7148   $174.71   $174.70   $174.70  
  7 purchase totals = $976.53       $1,054.6134   $1,054.61   $1,054.60   $1,054.60