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	$83.46	10.400%	$92.1398	$92.14	$92.15	$92.10
Purchase #2	$33.70	10.435%	$37.2166	$37.22	$37.20	$37.20
Purchase #3	$33.64	8.281%	$36.4257	$36.43	$36.45	$36.40
Purchase #4	$34.42	9.721%	$37.766	$37.77	$37.75	$37.80
Purchase #5	$83.99	9.448%	$91.9254	$91.93	$91.95	$91.90
Purchase #6	$53.97	9.640%	$59.1727	$59.17	$59.15	$59.20
Purchase #7	$16.72	5.132%	$17.5781	$17.58	$17.60	$17.60
7 purchase totals =	$339.90		$372.2243	$372.24	$372.25	$372.20