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	$104.80	6.500%	$111.612	$111.61	$111.60	$111.60
Purchase #2	$142.95	3.519%	$147.9804	$147.98	$148.00	$148.00
Purchase #3	$92.48	9.473%	$101.2406	$101.24	$101.25	$101.20
Purchase #4	$231.27	10.370%	$255.2527	$255.25	$255.25	$255.30
Purchase #5	$64.46	12.797%	$72.7089	$72.71	$72.70	$72.70
Purchase #6	$215.52	4.309%	$224.8068	$224.81	$224.80	$224.80
Purchase #7	$59.43	5.383%	$62.6291	$62.63	$62.65	$62.60
7 purchase totals =	$910.91		$976.2305	$976.23	$976.25	$976.20