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	$207.27	7.722%	$223.2754	$223.28	$223.30	$223.30
Purchase #2	$51.90	7.448%	$55.7655	$55.77	$55.75	$55.80
Purchase #3	$88.94	4.472%	$92.9174	$92.92	$92.90	$92.90
Purchase #4	$199.46	12.530%	$224.4523	$224.45	$224.45	$224.50
Purchase #5	$205.71	11.560%	$229.4901	$229.49	$229.50	$229.50
Purchase #6	$172.95	7.643%	$186.1686	$186.17	$186.15	$186.20
Purchase #7	$39.46	6.707%	$42.1066	$42.11	$42.10	$42.10
7 purchase totals =	$965.69		$1,054.1759	$1,054.19	$1,054.15	$1,054.30