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	$195.48	9.416%	$213.8864	$213.89	$213.90	$213.90
Purchase #2	$39.75	13.617%	$45.1628	$45.16	$45.15	$45.20
Purchase #3	$173.56	8.111%	$187.6375	$187.64	$187.65	$187.60
Purchase #4	$95.78	3.494%	$99.1266	$99.13	$99.15	$99.10
Purchase #5	$143.74	4.858%	$150.7229	$150.72	$150.70	$150.70
Purchase #6	$72.94	6.564%	$77.7278	$77.73	$77.75	$77.70
Purchase #7	$50.87	13.235%	$57.6026	$57.60	$57.60	$57.60
7 purchase totals =	$772.12		$831.8666	$831.87	$831.90	$831.80