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 $184.64   11.431%   $205.7462   $205.75   $205.75   $205.70  
  Purchase #2 $239.44   13.210%   $271.07   $271.07   $271.05   $271.10  
  Purchase #3 $62.71   4.547%   $65.5614   $65.56   $65.55   $65.60  
  Purchase #4 $206.54   12.653%   $232.6735   $232.67   $232.65   $232.70  
  Purchase #5 $187.92   7.142%   $201.3412   $201.34   $201.35   $201.30  
  Purchase #6 $44.72   5.269%   $47.0763   $47.08   $47.10   $47.10  
  Purchase #7 $76.30   8.717%   $82.9511   $82.95   $82.95   $83.00  
  7 purchase totals = $1,002.27       $1,106.4197   $1,106.42   $1,106.40   $1,106.50