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	$218.48	9.169%	$238.5124	$238.51	$238.50	$238.50
Purchase #2	$82.27	11.626%	$91.8347	$91.83	$91.85	$91.80
Purchase #3	$239.92	13.715%	$272.825	$272.83	$272.85	$272.80
Purchase #4	$205.40	4.620%	$214.8895	$214.89	$214.90	$214.90
Purchase #5	$211.50	10.764%	$234.2659	$234.27	$234.25	$234.30
Purchase #6	$230.45	4.200%	$240.1289	$240.13	$240.15	$240.10
Purchase #7	$54.46	5.147%	$57.2631	$57.26	$57.25	$57.30
7 purchase totals =	$1,242.48		$1,349.7195	$1,349.72	$1,349.75	$1,349.70