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	$190.98	4.369%	$199.3239	$199.32	$199.30	$199.30
Purchase #2	$161.42	7.688%	$173.83	$173.83	$173.85	$173.80
Purchase #3	$154.65	7.870%	$166.821	$166.82	$166.80	$166.80
Purchase #4	$140.40	7.852%	$151.4242	$151.42	$151.40	$151.40
Purchase #5	$248.66	13.189%	$281.4558	$281.46	$281.45	$281.50
Purchase #6	$113.46	13.429%	$128.6965	$128.70	$128.70	$128.70
Purchase #7	$179.91	6.340%	$191.3163	$191.32	$191.30	$191.30
7 purchase totals =	$1,189.48		$1,292.8677	$1,292.87	$1,292.80	$1,292.80