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	$67.57	6.591%	$72.0235	$72.02	$72.00	$72.00
Purchase #2	$57.48	6.657%	$61.3064	$61.31	$61.30	$61.30
Purchase #3	$11.85	10.166%	$13.0547	$13.05	$13.05	$13.10
Purchase #4	$103.42	4.247%	$107.8122	$107.81	$107.80	$107.80
Purchase #5	$170.96	10.318%	$188.5997	$188.60	$188.60	$188.60
Purchase #6	$154.44	10.712%	$170.9836	$170.98	$171.00	$171.00
Purchase #7	$173.68	10.849%	$192.5225	$192.52	$192.50	$192.50
7 purchase totals =	$739.40		$806.3026	$806.29	$806.25	$806.30