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	$190.78	8.203%	$206.4297	$206.43	$206.45	$206.40
Purchase #2	$166.32	5.750%	$175.8834	$175.88	$175.90	$175.90
Purchase #3	$24.31	6.842%	$25.9733	$25.97	$25.95	$26.00
Purchase #4	$95.27	5.345%	$100.3622	$100.36	$100.35	$100.40
Purchase #5	$67.51	3.213%	$69.6791	$69.68	$69.70	$69.70
Purchase #6	$91.30	8.716%	$99.2577	$99.26	$99.25	$99.30
Purchase #7	$109.76	8.320%	$118.892	$118.89	$118.90	$118.90
7 purchase totals =	$745.25		$796.4774	$796.47	$796.50	$796.60