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	$211.57	5.151%	$222.468	$222.47	$222.45	$222.50
Purchase #2	$78.59	11.455%	$87.5925	$87.59	$87.60	$87.60
Purchase #3	$97.29	8.361%	$105.4244	$105.42	$105.40	$105.40
Purchase #4	$188.41	12.481%	$211.9255	$211.93	$211.95	$211.90
Purchase #5	$6.92	10.763%	$7.6648	$7.66	$7.65	$7.70
Purchase #6	$174.42	10.207%	$192.223	$192.22	$192.20	$192.20
Purchase #7	$239.63	5.795%	$253.5166	$253.52	$253.50	$253.50
7 purchase totals =	$996.83		$1,080.8148	$1,080.81	$1,080.75	$1,080.80