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	$175.46	5.607%	$185.298	$185.30	$185.30	$185.30
Purchase #2	$167.53	4.618%	$175.2665	$175.27	$175.25	$175.30
Purchase #3	$58.54	13.248%	$66.2954	$66.30	$66.30	$66.30
Purchase #4	$61.64	7.798%	$66.4467	$66.45	$66.45	$66.40
Purchase #5	$127.56	13.137%	$144.3176	$144.32	$144.30	$144.30
Purchase #6	$193.38	7.754%	$208.3747	$208.37	$208.35	$208.40
Purchase #7	$135.40	5.263%	$142.5261	$142.53	$142.55	$142.50
7 purchase totals =	$919.51		$988.5250	$988.54	$988.50	$988.50