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	$189.39	3.771%	$196.5319	$196.53	$196.55	$196.50
Purchase #2	$147.79	13.182%	$167.2717	$167.27	$167.25	$167.30
Purchase #3	$83.76	11.123%	$93.0766	$93.08	$93.10	$93.10
Purchase #4	$214.73	9.243%	$234.5775	$234.58	$234.60	$234.60
Purchase #5	$134.74	11.607%	$150.3793	$150.38	$150.40	$150.40
Purchase #6	$92.82	4.710%	$97.1918	$97.19	$97.20	$97.20
Purchase #7	$39.40	9.698%	$43.221	$43.22	$43.20	$43.20
7 purchase totals =	$902.63		$982.2498	$982.25	$982.30	$982.30