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 $173.70   11.641%   $193.9204   $193.92   $193.90   $193.90  
  Purchase #2 $98.45   8.732%   $107.0467   $107.05   $107.05   $107.00  
  Purchase #3 $9.90   8.315%   $10.7232   $10.72   $10.70   $10.70  
  Purchase #4 $243.61   9.643%   $267.1013   $267.10   $267.10   $267.10  
  Purchase #5 $119.86   5.352%   $126.2749   $126.27   $126.25   $126.30  
  Purchase #6 $183.61   3.396%   $189.8454   $189.85   $189.85   $189.80  
  Purchase #7 $200.86   5.142%   $211.1882   $211.19   $211.20   $211.20  
  7 purchase totals = $1,029.99       $1,106.1001   $1,106.10   $1,106.05   $1,106.00