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	$78.50	10.216%	$86.5196	$86.52	$86.50	$86.50
Purchase #2	$240.54	4.540%	$251.4605	$251.46	$251.45	$251.50
Purchase #3	$108.77	6.762%	$116.125	$116.13	$116.15	$116.10
Purchase #4	$83.28	10.143%	$91.7271	$91.73	$91.75	$91.70
Purchase #5	$153.58	13.790%	$174.7587	$174.76	$174.75	$174.80
Purchase #6	$59.28	11.726%	$66.2312	$66.23	$66.25	$66.20
Purchase #7	$133.65	13.153%	$151.229	$151.23	$151.25	$151.20
7 purchase totals =	$857.60		$938.0511	$938.06	$938.10	$938.00