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	$233.27	13.359%	$264.4325	$264.43	$264.45	$264.40
Purchase #2	$152.90	3.734%	$158.6093	$158.61	$158.60	$158.60
Purchase #3	$220.74	4.486%	$230.6424	$230.64	$230.65	$230.60
Purchase #4	$203.69	7.763%	$219.5025	$219.50	$219.50	$219.50
Purchase #5	$175.98	11.441%	$196.1139	$196.11	$196.10	$196.10
Purchase #6	$83.87	4.498%	$87.6425	$87.64	$87.65	$87.60
Purchase #7	$19.44	13.692%	$22.1017	$22.10	$22.10	$22.10
7 purchase totals =	$1,089.89		$1,179.0448	$1,179.03	$1,179.05	$1,178.90