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	$37.36	10.107%	$41.136	$41.14	$41.15	$41.10
Purchase #2	$128.62	12.695%	$144.9483	$144.95	$144.95	$144.90
Purchase #3	$111.28	13.195%	$125.9634	$125.96	$125.95	$126.00
Purchase #4	$235.58	8.543%	$255.7056	$255.71	$255.70	$255.70
Purchase #5	$66.25	9.814%	$72.7518	$72.75	$72.75	$72.80
Purchase #6	$193.64	13.645%	$220.0622	$220.06	$220.05	$220.10
Purchase #7	$244.28	4.761%	$255.9102	$255.91	$255.90	$255.90
7 purchase totals =	$1,017.01		$1,116.4775	$1,116.48	$1,116.45	$1,116.50