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	$118.64	7.475%	$127.5083	$127.51	$127.50	$127.50
Purchase #2	$87.95	7.341%	$94.4064	$94.41	$94.40	$94.40
Purchase #3	$164.93	12.594%	$185.7013	$185.70	$185.70	$185.70
Purchase #4	$222.28	5.126%	$233.6741	$233.67	$233.65	$233.70
Purchase #5	$19.41	9.683%	$21.2895	$21.29	$21.30	$21.30
Purchase #6	$33.71	5.211%	$35.4666	$35.47	$35.45	$35.50
Purchase #7	$180.90	9.138%	$197.4306	$197.43	$197.45	$197.40
7 purchase totals =	$827.82		$895.4768	$895.48	$895.45	$895.50