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	$130.90	12.711%	$147.5387	$147.54	$147.55	$147.50
Purchase #2	$97.65	9.523%	$106.9492	$106.95	$106.95	$106.90
Purchase #3	$134.88	3.132%	$139.1044	$139.10	$139.10	$139.10
Purchase #4	$90.60	10.472%	$100.0876	$100.09	$100.10	$100.10
Purchase #5	$233.43	10.232%	$257.3146	$257.31	$257.30	$257.30
Purchase #6	$61.44	10.553%	$67.9238	$67.92	$67.90	$67.90
Purchase #7	$146.97	12.858%	$165.8674	$165.87	$165.85	$165.90
7 purchase totals =	$895.87		$984.7857	$984.78	$984.75	$984.70