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	$139.59	8.345%	$151.2388	$151.24	$151.25	$151.20
Purchase #2	$166.58	8.786%	$181.2157	$181.22	$181.20	$181.20
Purchase #3	$158.94	6.831%	$169.7972	$169.80	$169.80	$169.80
Purchase #4	$60.40	4.297%	$62.9954	$63.00	$63.00	$63.00
Purchase #5	$77.28	13.817%	$87.9578	$87.96	$87.95	$88.00
Purchase #6	$175.96	8.360%	$190.6703	$190.67	$190.65	$190.70
Purchase #7	$233.67	9.380%	$255.5882	$255.59	$255.60	$255.60
7 purchase totals =	$1,012.42		$1,099.4634	$1,099.48	$1,099.45	$1,099.50