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	$242.29	9.757%	$265.9302	$265.93	$265.95	$265.90
Purchase #2	$19.41	11.487%	$21.6396	$21.64	$21.65	$21.60
Purchase #3	$83.25	6.751%	$88.8702	$88.87	$88.85	$88.90
Purchase #4	$164.74	6.528%	$175.4942	$175.49	$175.50	$175.50
Purchase #5	$54.50	6.164%	$57.8594	$57.86	$57.85	$57.90
Purchase #6	$173.44	8.741%	$188.6004	$188.60	$188.60	$188.60
Purchase #7	$96.54	13.214%	$109.2968	$109.30	$109.30	$109.30
7 purchase totals =	$834.17		$907.6908	$907.69	$907.70	$907.70