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	$169.72	13.649%	$192.8851	$192.89	$192.90	$192.90
Purchase #2	$161.77	6.636%	$172.5051	$172.51	$172.50	$172.50
Purchase #3	$94.46	11.828%	$105.6327	$105.63	$105.65	$105.60
Purchase #4	$22.94	5.399%	$24.1785	$24.18	$24.20	$24.20
Purchase #5	$114.51	4.416%	$119.5668	$119.57	$119.55	$119.60
Purchase #6	$18.72	4.160%	$19.4988	$19.50	$19.50	$19.50
Purchase #7	$64.40	12.238%	$72.2813	$72.28	$72.30	$72.30
7 purchase totals =	$646.52		$706.5483	$706.56	$706.60	$706.60