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	$153.89	5.373%	$162.1585	$162.16	$162.15	$162.20
Purchase #2	$138.89	7.687%	$149.5665	$149.57	$149.55	$149.60
Purchase #3	$153.66	3.236%	$158.6324	$158.63	$158.65	$158.60
Purchase #4	$217.90	9.834%	$239.3283	$239.33	$239.35	$239.30
Purchase #5	$144.55	5.468%	$152.454	$152.45	$152.45	$152.50
Purchase #6	$96.33	4.404%	$100.5724	$100.57	$100.55	$100.60
Purchase #7	$182.53	4.379%	$190.523	$190.52	$190.50	$190.50
7 purchase totals =	$1,087.75		$1,153.2351	$1,153.23	$1,153.20	$1,153.30