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	$122.65	13.522%	$139.2347	$139.23	$139.25	$139.20
Purchase #2	$134.97	13.800%	$153.5959	$153.60	$153.60	$153.60
Purchase #3	$157.52	6.211%	$167.3036	$167.30	$167.30	$167.30
Purchase #4	$227.77	11.213%	$253.3099	$253.31	$253.30	$253.30
Purchase #5	$189.37	8.601%	$205.6577	$205.66	$205.65	$205.70
Purchase #6	$210.93	4.267%	$219.9304	$219.93	$219.95	$219.90
Purchase #7	$54.34	9.206%	$59.3425	$59.34	$59.35	$59.30
7 purchase totals =	$1,097.55		$1,198.3747	$1,198.37	$1,198.40	$1,198.30