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	$132.61	10.375%	$146.3683	$146.37	$146.35	$146.40
Purchase #2	$192.26	5.403%	$202.6478	$202.65	$202.65	$202.60
Purchase #3	$62.77	13.849%	$71.463	$71.46	$71.45	$71.50
Purchase #4	$225.49	7.426%	$242.2349	$242.23	$242.25	$242.20
Purchase #5	$65.55	11.167%	$72.87	$72.87	$72.85	$72.90
Purchase #6	$109.69	9.771%	$120.4078	$120.41	$120.40	$120.40
Purchase #7	$145.30	11.574%	$162.117	$162.12	$162.10	$162.10
7 purchase totals =	$933.67		$1,018.1088	$1,018.11	$1,018.05	$1,018.10