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	$80.60	6.240%	$85.6294	$85.63	$85.65	$85.60
Purchase #2	$7.57	12.115%	$8.4871	$8.49	$8.50	$8.50
Purchase #3	$61.52	6.188%	$65.3269	$65.33	$65.35	$65.30
Purchase #4	$171.86	5.410%	$181.1576	$181.16	$181.15	$181.20
Purchase #5	$62.78	12.321%	$70.5151	$70.52	$70.50	$70.50
Purchase #6	$20.52	10.420%	$22.6582	$22.66	$22.65	$22.70
Purchase #7	$211.43	10.545%	$233.7253	$233.73	$233.75	$233.70
7 purchase totals =	$616.28		$667.4996	$667.52	$667.55	$667.50