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	$145.25	9.142%	$158.5288	$158.53	$158.55	$158.50
Purchase #2	$61.88	8.248%	$66.9839	$66.98	$67.00	$67.00
Purchase #3	$64.86	8.832%	$70.5884	$70.59	$70.60	$70.60
Purchase #4	$85.30	5.539%	$90.0248	$90.02	$90.00	$90.00
Purchase #5	$113.96	4.237%	$118.7885	$118.79	$118.80	$118.80
Purchase #6	$174.77	8.326%	$189.3214	$189.32	$189.30	$189.30
Purchase #7	$49.27	4.404%	$51.4399	$51.44	$51.45	$51.40
7 purchase totals =	$695.29		$745.6757	$745.67	$745.70	$745.60