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	$100.63	12.501%	$113.2098	$113.21	$113.20	$113.20
Purchase #2	$117.46	13.158%	$132.9154	$132.92	$132.90	$132.90
Purchase #3	$165.27	6.631%	$176.2291	$176.23	$176.25	$176.20
Purchase #4	$48.48	4.605%	$50.7125	$50.71	$50.70	$50.70
Purchase #5	$118.54	10.701%	$131.225	$131.23	$131.25	$131.20
Purchase #6	$124.52	4.782%	$130.4745	$130.47	$130.45	$130.50
Purchase #7	$231.82	11.866%	$259.3278	$259.33	$259.35	$259.30
7 purchase totals =	$906.72		$994.0941	$994.10	$994.10	$994.00