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	$140.29	11.717%	$156.7278	$156.73	$156.75	$156.70
Purchase #2	$127.94	10.595%	$141.4952	$141.50	$141.50	$141.50
Purchase #3	$92.61	10.185%	$102.0423	$102.04	$102.05	$102.00
Purchase #4	$69.60	8.334%	$75.4005	$75.40	$75.40	$75.40
Purchase #5	$241.93	11.365%	$269.4253	$269.43	$269.45	$269.40
Purchase #6	$83.53	9.528%	$91.4887	$91.49	$91.50	$91.50
Purchase #7	$95.92	6.160%	$101.8287	$101.83	$101.85	$101.80
7 purchase totals =	$851.82		$938.4085	$938.42	$938.50	$938.30