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	$207.43	7.724%	$223.4519	$223.45	$223.45	$223.50
Purchase #2	$233.95	7.680%	$251.9174	$251.92	$251.90	$251.90
Purchase #3	$184.46	4.323%	$192.4342	$192.43	$192.45	$192.40
Purchase #4	$63.30	13.179%	$71.6423	$71.64	$71.65	$71.60
Purchase #5	$164.56	9.164%	$179.6403	$179.64	$179.65	$179.60
Purchase #6	$11.39	7.776%	$12.2757	$12.28	$12.30	$12.30
Purchase #7	$142.40	11.821%	$159.2331	$159.23	$159.25	$159.20
7 purchase totals =	$1,007.49		$1,090.5949	$1,090.59	$1,090.65	$1,090.50