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	$218.51	10.815%	$242.1419	$242.14	$242.15	$242.10
Purchase #2	$42.95	8.151%	$46.4509	$46.45	$46.45	$46.50
Purchase #3	$145.86	3.673%	$151.2174	$151.22	$151.20	$151.20
Purchase #4	$150.33	9.608%	$164.7737	$164.77	$164.75	$164.80
Purchase #5	$188.94	8.570%	$205.1322	$205.13	$205.15	$205.10
Purchase #6	$132.57	12.543%	$149.1983	$149.20	$149.20	$149.20
Purchase #7	$51.61	5.383%	$54.3882	$54.39	$54.40	$54.40
7 purchase totals =	$930.77		$1,013.3026	$1,013.30	$1,013.30	$1,013.30