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	$111.53	4.463%	$116.5076	$116.51	$116.50	$116.50
Purchase #2	$54.90	4.365%	$57.2964	$57.30	$57.30	$57.30
Purchase #3	$133.69	8.779%	$145.4266	$145.43	$145.45	$145.40
Purchase #4	$30.86	4.559%	$32.2669	$32.27	$32.25	$32.30
Purchase #5	$74.41	12.648%	$83.8214	$83.82	$83.80	$83.80
Purchase #6	$124.97	7.444%	$134.2728	$134.27	$134.25	$134.30
Purchase #7	$152.96	4.421%	$159.7224	$159.72	$159.70	$159.70
7 purchase totals =	$683.32		$729.3141	$729.32	$729.25	$729.30