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	$167.74	10.617%	$185.549	$185.55	$185.55	$185.50
Purchase #2	$179.99	11.578%	$200.8292	$200.83	$200.85	$200.80
Purchase #3	$54.53	8.861%	$59.3619	$59.36	$59.35	$59.40
Purchase #4	$220.62	3.385%	$228.088	$228.09	$228.10	$228.10
Purchase #5	$12.42	5.772%	$13.1369	$13.14	$13.15	$13.10
Purchase #6	$184.27	3.724%	$191.1322	$191.13	$191.15	$191.10
Purchase #7	$53.63	3.276%	$55.3869	$55.39	$55.40	$55.40
7 purchase totals =	$873.20		$933.4841	$933.49	$933.55	$933.40