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	$157.43	7.659%	$169.4876	$169.49	$169.50	$169.50
Purchase #2	$95.28	11.161%	$105.9142	$105.91	$105.90	$105.90
Purchase #3	$95.64	4.164%	$99.6224	$99.62	$99.60	$99.60
Purchase #4	$18.62	10.384%	$20.5535	$20.55	$20.55	$20.60
Purchase #5	$13.47	5.578%	$14.2214	$14.22	$14.20	$14.20
Purchase #6	$135.26	8.608%	$146.9032	$146.90	$146.90	$146.90
Purchase #7	$205.43	11.603%	$229.266	$229.27	$229.25	$229.30
7 purchase totals =	$721.13		$785.9683	$785.96	$785.90	$786.00