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	$67.26	13.171%	$76.1188	$76.12	$76.10	$76.10
Purchase #2	$184.82	7.394%	$198.4856	$198.49	$198.50	$198.50
Purchase #3	$126.32	3.790%	$131.1075	$131.11	$131.10	$131.10
Purchase #4	$174.92	12.560%	$196.89	$196.89	$196.90	$196.90
Purchase #5	$14.91	10.222%	$16.4341	$16.43	$16.45	$16.40
Purchase #6	$174.91	10.501%	$193.2773	$193.28	$193.30	$193.30
Purchase #7	$87.64	13.673%	$99.623	$99.62	$99.60	$99.60
7 purchase totals =	$830.78		$911.9363	$911.94	$911.95	$911.90