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	$74.57	4.237%	$77.7295	$77.73	$77.75	$77.70
Purchase #2	$106.70	6.517%	$113.6536	$113.65	$113.65	$113.70
Purchase #3	$69.73	13.832%	$79.3751	$79.38	$79.40	$79.40
Purchase #4	$131.92	11.192%	$146.6845	$146.68	$146.70	$146.70
Purchase #5	$84.72	5.630%	$89.4897	$89.49	$89.50	$89.50
Purchase #6	$229.66	10.349%	$253.4275	$253.43	$253.45	$253.40
Purchase #7	$188.50	4.112%	$196.2511	$196.25	$196.25	$196.30
7 purchase totals =	$885.80		$956.6110	$956.61	$956.70	$956.70