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	$89.33	10.569%	$98.7713	$98.77	$98.75	$98.80
Purchase #2	$184.72	8.520%	$200.4581	$200.46	$200.45	$200.50
Purchase #3	$68.56	12.506%	$77.1341	$77.13	$77.15	$77.10
Purchase #4	$180.50	7.404%	$193.8642	$193.86	$193.85	$193.90
Purchase #5	$226.68	6.708%	$241.8857	$241.89	$241.90	$241.90
Purchase #6	$152.64	4.485%	$159.4859	$159.49	$159.50	$159.50
Purchase #7	$154.92	12.212%	$173.8388	$173.84	$173.85	$173.80
7 purchase totals =	$1,057.35		$1,145.4381	$1,145.44	$1,145.45	$1,145.50