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	$87.40	12.698%	$98.4981	$98.50	$98.50	$98.50
Purchase #2	$159.27	12.250%	$178.7806	$178.78	$178.80	$178.80
Purchase #3	$33.65	12.622%	$37.8973	$37.90	$37.90	$37.90
Purchase #4	$10.35	7.847%	$11.1622	$11.16	$11.15	$11.20
Purchase #5	$116.27	9.825%	$127.6935	$127.69	$127.70	$127.70
Purchase #6	$224.77	8.840%	$244.6397	$244.64	$244.65	$244.60
Purchase #7	$167.93	3.762%	$174.2475	$174.25	$174.25	$174.20
7 purchase totals =	$799.64		$872.9189	$872.92	$872.95	$872.90