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	$87.66	12.335%	$98.4729	$98.47	$98.45	$98.50
Purchase #2	$169.73	8.435%	$184.0467	$184.05	$184.05	$184.00
Purchase #3	$13.87	7.563%	$14.919	$14.92	$14.90	$14.90
Purchase #4	$78.80	4.748%	$82.5414	$82.54	$82.55	$82.50
Purchase #5	$82.94	13.317%	$93.9851	$93.99	$94.00	$94.00
Purchase #6	$133.99	13.784%	$152.4592	$152.46	$152.45	$152.50
Purchase #7	$107.63	3.236%	$111.1129	$111.11	$111.10	$111.10
7 purchase totals =	$674.62		$737.5372	$737.54	$737.50	$737.50