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	$177.54	4.869%	$186.1844	$186.18	$186.20	$186.20
Purchase #2	$29.83	6.775%	$31.851	$31.85	$31.85	$31.90
Purchase #3	$99.26	9.240%	$108.4316	$108.43	$108.45	$108.40
Purchase #4	$146.47	3.700%	$151.8894	$151.89	$151.90	$151.90
Purchase #5	$230.29	6.612%	$245.5168	$245.52	$245.50	$245.50
Purchase #6	$12.45	13.325%	$14.109	$14.11	$14.10	$14.10
Purchase #7	$28.87	3.475%	$29.8732	$29.87	$29.85	$29.90
7 purchase totals =	$724.71		$767.8554	$767.85	$767.85	$767.90