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	$175.44	5.250%	$184.6506	$184.65	$184.65	$184.70
Purchase #2	$207.69	10.788%	$230.0956	$230.10	$230.10	$230.10
Purchase #3	$56.28	4.848%	$59.0085	$59.01	$59.00	$59.00
Purchase #4	$151.91	13.630%	$172.6153	$172.62	$172.60	$172.60
Purchase #5	$233.65	5.512%	$246.5288	$246.53	$246.55	$246.50
Purchase #6	$110.69	8.526%	$120.1274	$120.13	$120.15	$120.10
Purchase #7	$62.25	8.181%	$67.3427	$67.34	$67.35	$67.30
7 purchase totals =	$997.91		$1,080.3689	$1,080.38	$1,080.40	$1,080.30