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	$179.68	11.417%	$200.1941	$200.19	$200.20	$200.20
Purchase #2	$91.92	6.378%	$97.7827	$97.78	$97.80	$97.80
Purchase #3	$92.78	8.320%	$100.4993	$100.50	$100.50	$100.50
Purchase #4	$142.72	12.222%	$160.1632	$160.16	$160.15	$160.20
Purchase #5	$172.88	7.541%	$185.9169	$185.92	$185.90	$185.90
Purchase #6	$127.96	5.377%	$134.8404	$134.84	$134.85	$134.80
Purchase #7	$59.83	3.794%	$62.1	$62.10	$62.10	$62.10
7 purchase totals =	$867.77		$941.4966	$941.49	$941.50	$941.50