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	$61.45	6.860%	$65.6655	$65.67	$65.65	$65.70
Purchase #2	$199.80	11.339%	$222.4553	$222.46	$222.45	$222.50
Purchase #3	$153.72	13.316%	$174.1894	$174.19	$174.20	$174.20
Purchase #4	$56.55	5.805%	$59.8327	$59.83	$59.85	$59.80
Purchase #5	$59.51	13.339%	$67.448	$67.45	$67.45	$67.40
Purchase #6	$130.30	10.639%	$144.1626	$144.16	$144.15	$144.20
Purchase #7	$78.61	3.845%	$81.6326	$81.63	$81.65	$81.60
7 purchase totals =	$739.94		$815.3861	$815.39	$815.40	$815.40