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	$249.79	3.321%	$258.0855	$258.09	$258.10	$258.10
Purchase #2	$152.34	13.215%	$172.4717	$172.47	$172.45	$172.50
Purchase #3	$85.63	7.600%	$92.1379	$92.14	$92.15	$92.10
Purchase #4	$91.86	4.815%	$96.2831	$96.28	$96.30	$96.30
Purchase #5	$98.34	6.614%	$104.8442	$104.84	$104.85	$104.80
Purchase #6	$118.52	6.391%	$126.0946	$126.09	$126.10	$126.10
Purchase #7	$176.47	8.573%	$191.5988	$191.60	$191.60	$191.60
7 purchase totals =	$972.95		$1,041.5158	$1,041.51	$1,041.55	$1,041.50