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 $65.36   11.107%   $72.6195   $72.62   $72.60   $72.60  
  Purchase #2 $87.94   9.340%   $96.1536   $96.15   $96.15   $96.20  
  Purchase #3 $202.78   10.409%   $223.8874   $223.89   $223.90   $223.90  
  Purchase #4 $108.25   4.696%   $113.3334   $113.33   $113.35   $113.30  
  Purchase #5 $186.68   10.799%   $206.8396   $206.84   $206.85   $206.80  
  Purchase #6 $105.83   9.621%   $116.0119   $116.01   $116.00   $116.00  
  Purchase #7 $113.54   6.116%   $120.4841   $120.48   $120.50   $120.50  
  7 purchase totals = $870.38       $949.3295   $949.32   $949.35   $949.30