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	$147.77	11.269%	$164.4222	$164.42	$164.40	$164.40
Purchase #2	$172.41	4.542%	$180.2409	$180.24	$180.25	$180.20
Purchase #3	$233.42	9.544%	$255.6976	$255.70	$255.70	$255.70
Purchase #4	$192.92	8.109%	$208.5639	$208.56	$208.55	$208.60
Purchase #5	$37.93	7.210%	$40.6648	$40.66	$40.65	$40.70
Purchase #6	$152.59	5.361%	$160.7703	$160.77	$160.75	$160.80
Purchase #7	$99.50	6.136%	$105.6053	$105.61	$105.60	$105.60
7 purchase totals =	$1,036.54		$1,115.9650	$1,115.96	$1,115.90	$1,116.00