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	$66.48	13.216%	$75.266	$75.27	$75.25	$75.30
Purchase #2	$56.65	3.246%	$58.4889	$58.49	$58.50	$58.50
Purchase #3	$234.95	4.772%	$246.1618	$246.16	$246.15	$246.20
Purchase #4	$242.58	8.271%	$262.6438	$262.64	$262.65	$262.60
Purchase #5	$111.82	13.667%	$127.1024	$127.10	$127.10	$127.10
Purchase #6	$119.55	7.460%	$128.4684	$128.47	$128.45	$128.50
Purchase #7	$196.61	7.393%	$211.1454	$211.15	$211.15	$211.10
7 purchase totals =	$1,028.64		$1,109.2767	$1,109.28	$1,109.25	$1,109.30