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	$61.95	13.681%	$70.4254	$70.43	$70.45	$70.40
Purchase #2	$23.83	11.192%	$26.4971	$26.50	$26.50	$26.50
Purchase #3	$139.53	6.415%	$148.4808	$148.48	$148.50	$148.50
Purchase #4	$69.37	3.615%	$71.8777	$71.88	$71.90	$71.90
Purchase #5	$143.50	13.178%	$162.4104	$162.41	$162.40	$162.40
Purchase #6	$118.67	7.388%	$127.4373	$127.44	$127.45	$127.40
Purchase #7	$115.50	5.548%	$121.9079	$121.91	$121.90	$121.90
7 purchase totals =	$672.35		$729.0366	$729.05	$729.10	$729.00