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	$10.83	4.607%	$11.3289	$11.33	$11.35	$11.30
Purchase #2	$49.42	9.721%	$54.2241	$54.22	$54.20	$54.20
Purchase #3	$81.77	11.374%	$91.0705	$91.07	$91.05	$91.10
Purchase #4	$250.97	13.596%	$285.0919	$285.09	$285.10	$285.10
Purchase #5	$182.49	12.832%	$205.9071	$205.91	$205.90	$205.90
Purchase #6	$210.58	8.798%	$229.1068	$229.11	$229.10	$229.10
Purchase #7	$211.35	11.298%	$235.2283	$235.23	$235.25	$235.20
7 purchase totals =	$997.41		$1,111.9576	$1,111.96	$1,111.95	$1,111.90