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	$209.64	9.376%	$229.2958	$229.30	$229.30	$229.30
Purchase #2	$244.89	4.694%	$256.3851	$256.39	$256.40	$256.40
Purchase #3	$87.27	3.539%	$90.3585	$90.36	$90.35	$90.40
Purchase #4	$140.76	13.165%	$159.2911	$159.29	$159.30	$159.30
Purchase #5	$178.46	10.547%	$197.2822	$197.28	$197.30	$197.30
Purchase #6	$211.72	8.150%	$228.9752	$228.98	$229.00	$229.00
Purchase #7	$80.77	9.667%	$88.578	$88.58	$88.60	$88.60
7 purchase totals =	$1,153.51		$1,250.1659	$1,250.18	$1,250.25	$1,250.30