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	$86.29	4.838%	$90.4647	$90.46	$90.45	$90.50
Purchase #2	$173.66	12.643%	$195.6158	$195.62	$195.60	$195.60
Purchase #3	$177.46	4.651%	$185.7137	$185.71	$185.70	$185.70
Purchase #4	$191.94	6.518%	$204.4506	$204.45	$204.45	$204.50
Purchase #5	$206.27	5.530%	$217.6767	$217.68	$217.70	$217.70
Purchase #6	$179.98	11.471%	$200.6255	$200.63	$200.65	$200.60
Purchase #7	$167.38	4.465%	$174.8535	$174.85	$174.85	$174.90
7 purchase totals =	$1,182.98		$1,269.4005	$1,269.40	$1,269.40	$1,269.50