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	$185.75	8.688%	$201.888	$201.89	$201.90	$201.90
Purchase #2	$229.81	12.592%	$258.7477	$258.75	$258.75	$258.70
Purchase #3	$141.79	6.829%	$151.4728	$151.47	$151.45	$151.50
Purchase #4	$45.81	6.208%	$48.6539	$48.65	$48.65	$48.70
Purchase #5	$96.80	3.586%	$100.2712	$100.27	$100.25	$100.30
Purchase #6	$132.75	10.521%	$146.7166	$146.72	$146.70	$146.70
Purchase #7	$96.27	3.857%	$99.9831	$99.98	$100.00	$100.00
7 purchase totals =	$928.98		$1,007.7333	$1,007.73	$1,007.70	$1,007.80