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	$206.50	8.237%	$223.5094	$223.51	$223.50	$223.50
Purchase #2	$229.73	10.257%	$253.2934	$253.29	$253.30	$253.30
Purchase #3	$249.29	4.472%	$260.4382	$260.44	$260.45	$260.40
Purchase #4	$92.71	9.358%	$101.3858	$101.39	$101.40	$101.40
Purchase #5	$57.31	4.150%	$59.6884	$59.69	$59.70	$59.70
Purchase #6	$250.32	7.224%	$268.4031	$268.40	$268.40	$268.40
Purchase #7	$8.92	13.354%	$10.1112	$10.11	$10.10	$10.10
7 purchase totals =	$1,094.78		$1,176.8295	$1,176.83	$1,176.85	$1,176.80