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	$133.93	8.607%	$145.4574	$145.46	$145.45	$145.50
Purchase #2	$118.34	4.506%	$123.6724	$123.67	$123.65	$123.70
Purchase #3	$213.58	9.627%	$234.1413	$234.14	$234.15	$234.10
Purchase #4	$56.44	6.134%	$59.902	$59.90	$59.90	$59.90
Purchase #5	$111.83	3.152%	$115.3549	$115.35	$115.35	$115.40
Purchase #6	$140.60	3.376%	$145.3467	$145.35	$145.35	$145.30
Purchase #7	$63.75	4.517%	$66.6296	$66.63	$66.65	$66.60
7 purchase totals =	$838.47		$890.5043	$890.50	$890.50	$890.50