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	$184.68	4.667%	$193.299	$193.30	$193.30	$193.30
Purchase #2	$175.51	7.212%	$188.1678	$188.17	$188.15	$188.20
Purchase #3	$226.81	10.434%	$250.4754	$250.48	$250.50	$250.50
Purchase #4	$245.63	13.720%	$279.3304	$279.33	$279.35	$279.30
Purchase #5	$35.41	6.602%	$37.7478	$37.75	$37.75	$37.70
Purchase #6	$68.91	4.873%	$72.268	$72.27	$72.25	$72.30
Purchase #7	$172.66	9.550%	$189.149	$189.15	$189.15	$189.10
7 purchase totals =	$1,109.61		$1,210.4374	$1,210.45	$1,210.45	$1,210.40