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	$152.37	5.419%	$160.6269	$160.63	$160.65	$160.60
Purchase #2	$100.37	9.181%	$109.585	$109.59	$109.60	$109.60
Purchase #3	$159.67	7.865%	$172.228	$172.23	$172.25	$172.20
Purchase #4	$230.36	5.240%	$242.4309	$242.43	$242.45	$242.40
Purchase #5	$125.93	13.120%	$142.452	$142.45	$142.45	$142.50
Purchase #6	$85.71	7.854%	$92.4417	$92.44	$92.45	$92.40
Purchase #7	$249.56	11.191%	$277.4883	$277.49	$277.50	$277.50
7 purchase totals =	$1,103.97		$1,197.2528	$1,197.26	$1,197.35	$1,197.20