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 $12.87   10.590%   $14.2329   $14.23   $14.25   $14.20  
  Purchase #2 $87.98   8.599%   $95.5454   $95.55   $95.55   $95.50  
  Purchase #3 $91.70   9.374%   $100.296   $100.30   $100.30   $100.30  
  Purchase #4 $110.73   5.135%   $116.416   $116.42   $116.40   $116.40  
  Purchase #5 $53.78   9.550%   $58.916   $58.92   $58.90   $58.90  
  Purchase #6 $241.33   4.485%   $252.1537   $252.15   $252.15   $252.20  
  Purchase #7 $165.93   5.458%   $174.9865   $174.99   $175.00   $175.00  
  7 purchase totals = $764.32       $812.5465   $812.56   $812.55   $812.50