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	$47.55	12.384%	$53.4386	$53.44	$53.45	$53.40
Purchase #2	$99.35	13.588%	$112.8497	$112.85	$112.85	$112.80
Purchase #3	$10.28	11.450%	$11.4571	$11.46	$11.45	$11.50
Purchase #4	$41.73	9.318%	$45.6184	$45.62	$45.60	$45.60
Purchase #5	$96.39	11.146%	$107.1336	$107.13	$107.15	$107.10
Purchase #6	$88.30	12.582%	$99.4099	$99.41	$99.40	$99.40
Purchase #7	$22.44	11.406%	$24.9995	$25.00	$25.00	$25.00
7 purchase totals =	$406.04		$454.9068	$454.91	$454.90	$454.80