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	$142.60	4.801%	$149.4462	$149.45	$149.45	$149.40
Purchase #2	$70.74	8.558%	$76.7939	$76.79	$76.80	$76.80
Purchase #3	$68.94	13.839%	$78.4806	$78.48	$78.50	$78.50
Purchase #4	$89.65	11.459%	$99.923	$99.92	$99.90	$99.90
Purchase #5	$42.89	13.596%	$48.7213	$48.72	$48.70	$48.70
Purchase #6	$247.81	7.532%	$266.475	$266.48	$266.50	$266.50
Purchase #7	$93.66	3.873%	$97.2875	$97.29	$97.30	$97.30
7 purchase totals =	$756.29		$817.1275	$817.13	$817.15	$817.10