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	$192.47	9.677%	$211.0953	$211.10	$211.10	$211.10
Purchase #2	$83.35	7.844%	$89.888	$89.89	$89.90	$89.90
Purchase #3	$9.76	6.250%	$10.37	$10.37	$10.35	$10.40
Purchase #4	$118.87	6.435%	$126.5193	$126.52	$126.50	$126.50
Purchase #5	$187.88	3.385%	$194.2397	$194.24	$194.25	$194.20
Purchase #6	$156.91	5.238%	$165.1289	$165.13	$165.15	$165.10
Purchase #7	$172.64	9.826%	$189.6036	$189.60	$189.60	$189.60
7 purchase totals =	$921.88		$986.8448	$986.85	$986.85	$986.80