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	$151.72	4.811%	$159.0192	$159.02	$159.00	$159.00
Purchase #2	$160.54	3.204%	$165.6837	$165.68	$165.70	$165.70
Purchase #3	$55.51	7.403%	$59.6194	$59.62	$59.60	$59.60
Purchase #4	$160.25	7.511%	$172.2864	$172.29	$172.30	$172.30
Purchase #5	$199.88	3.598%	$207.0717	$207.07	$207.05	$207.10
Purchase #6	$109.53	4.476%	$114.4326	$114.43	$114.45	$114.40
Purchase #7	$239.58	3.676%	$248.387	$248.39	$248.40	$248.40
7 purchase totals =	$1,077.01		$1,126.5000	$1,126.50	$1,126.50	$1,126.50