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	$72.89	11.492%	$81.2665	$81.27	$81.25	$81.30
Purchase #2	$10.35	10.209%	$11.4066	$11.41	$11.40	$11.40
Purchase #3	$238.55	4.852%	$250.1244	$250.12	$250.10	$250.10
Purchase #4	$160.46	11.209%	$178.446	$178.45	$178.45	$178.40
Purchase #5	$149.26	4.250%	$155.6036	$155.60	$155.60	$155.60
Purchase #6	$122.45	5.508%	$129.1945	$129.19	$129.20	$129.20
Purchase #7	$184.97	6.326%	$196.6712	$196.67	$196.65	$196.70
7 purchase totals =	$938.93		$1,002.7128	$1,002.71	$1,002.65	$1,002.70