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	$149.54	7.501%	$160.757	$160.76	$160.75	$160.80
Purchase #2	$151.97	13.556%	$172.5711	$172.57	$172.55	$172.60
Purchase #3	$94.87	13.344%	$107.5295	$107.53	$107.55	$107.50
Purchase #4	$19.63	5.606%	$20.7305	$20.73	$20.75	$20.70
Purchase #5	$172.77	11.303%	$192.2982	$192.30	$192.30	$192.30
Purchase #6	$65.71	5.573%	$69.372	$69.37	$69.35	$69.40
Purchase #7	$90.37	11.670%	$100.9162	$100.92	$100.90	$100.90
7 purchase totals =	$744.86		$824.1745	$824.18	$824.15	$824.20