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 $210.75   10.653%   $233.2012   $233.20   $233.20   $233.20  
  Purchase #2 $162.43   8.620%   $176.4315   $176.43   $176.45   $176.40  
  Purchase #3 $67.47   11.733%   $75.3863   $75.39   $75.40   $75.40  
  Purchase #4 $165.63   9.341%   $181.1015   $181.10   $181.10   $181.10  
  Purchase #5 $214.71   8.696%   $233.3812   $233.38   $233.40   $233.40  
  Purchase #6 $107.87   11.472%   $120.2448   $120.24   $120.25   $120.20  
  Purchase #7 $36.51   11.115%   $40.5681   $40.57   $40.55   $40.60  
  7 purchase totals = $965.37       $1,060.3146   $1,060.31   $1,060.35   $1,060.30