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 $44.76   3.253%   $46.216   $46.22   $46.20   $46.20  
  Purchase #2 $102.40   8.658%   $111.2658   $111.27   $111.25   $111.30  
  Purchase #3 $15.52   7.415%   $16.6708   $16.67   $16.65   $16.70  
  Purchase #4 $104.31   13.714%   $118.6151   $118.62   $118.60   $118.60  
  Purchase #5 $116.63   5.814%   $123.4109   $123.41   $123.40   $123.40  
  Purchase #6 $241.74   11.687%   $269.9922   $269.99   $270.00   $270.00  
  Purchase #7 $247.95   10.494%   $273.9699   $273.97   $273.95   $274.00  
  7 purchase totals = $873.31       $960.1407   $960.15   $960.05   $960.20