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	$31.26	9.778%	$34.3166	$34.32	$34.30	$34.30
Purchase #2	$160.46	7.249%	$172.0917	$172.09	$172.10	$172.10
Purchase #3	$205.25	9.286%	$224.3095	$224.31	$224.30	$224.30
Purchase #4	$118.76	3.810%	$123.2848	$123.28	$123.30	$123.30
Purchase #5	$170.76	9.829%	$187.544	$187.54	$187.55	$187.50
Purchase #6	$198.51	11.860%	$222.0533	$222.05	$222.05	$222.10
Purchase #7	$195.37	4.862%	$204.8689	$204.87	$204.85	$204.90
7 purchase totals =	$1,080.37		$1,168.4688	$1,168.46	$1,168.45	$1,168.50