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	$77.94	9.712%	$85.5095	$85.51	$85.50	$85.50
Purchase #2	$209.38	9.624%	$229.5307	$229.53	$229.55	$229.50
Purchase #3	$239.32	13.241%	$271.0084	$271.01	$271.00	$271.00
Purchase #4	$184.76	6.230%	$196.2705	$196.27	$196.25	$196.30
Purchase #5	$111.92	6.164%	$118.8187	$118.82	$118.80	$118.80
Purchase #6	$239.56	9.565%	$262.4739	$262.47	$262.45	$262.50
Purchase #7	$51.33	4.569%	$53.6753	$53.68	$53.70	$53.70
7 purchase totals =	$1,114.21		$1,217.2870	$1,217.29	$1,217.25	$1,217.30