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 $60.26   9.527%   $66.001   $66.00   $66.00   $66.00  
  Purchase #2 $43.86   5.193%   $46.1376   $46.14   $46.15   $46.10  
  Purchase #3 $156.77   11.313%   $174.5054   $174.51   $174.50   $174.50  
  Purchase #4 $14.97   10.540%   $16.5478   $16.55   $16.55   $16.50  
  Purchase #5 $214.75   5.279%   $226.0867   $226.09   $226.10   $226.10  
  Purchase #6 $76.59   5.735%   $80.9824   $80.98   $81.00   $81.00  
  Purchase #7 $88.27   4.141%   $91.9253   $91.93   $91.95   $91.90  
  7 purchase totals = $655.47       $702.1862   $702.20   $702.25   $702.10