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	$229.71	3.713%	$238.2391	$238.24	$238.25	$238.20
Purchase #2	$105.78	7.103%	$113.2936	$113.29	$113.30	$113.30
Purchase #3	$46.60	10.532%	$51.5079	$51.51	$51.50	$51.50
Purchase #4	$28.85	3.532%	$29.869	$29.87	$29.85	$29.90
Purchase #5	$77.39	11.582%	$86.3533	$86.35	$86.35	$86.40
Purchase #6	$115.81	8.298%	$125.4199	$125.42	$125.40	$125.40
Purchase #7	$110.33	5.846%	$116.7799	$116.78	$116.80	$116.80
7 purchase totals =	$714.47		$761.4627	$761.46	$761.45	$761.50