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	$190.78	11.799%	$213.2901	$213.29	$213.30	$213.30
Purchase #2	$162.40	12.823%	$183.2246	$183.22	$183.20	$183.20
Purchase #3	$70.81	5.111%	$74.4291	$74.43	$74.45	$74.40
Purchase #4	$216.87	11.540%	$241.8968	$241.90	$241.90	$241.90
Purchase #5	$127.52	13.705%	$144.9966	$145.00	$145.00	$145.00
Purchase #6	$133.71	13.788%	$152.1459	$152.15	$152.15	$152.10
Purchase #7	$118.73	11.306%	$132.1536	$132.15	$132.15	$132.20
7 purchase totals =	$1,020.82		$1,142.1367	$1,142.14	$1,142.15	$1,142.10