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	$93.54	12.276%	$105.023	$105.02	$105.00	$105.00
Purchase #2	$113.52	4.297%	$118.398	$118.40	$118.40	$118.40
Purchase #3	$100.27	5.499%	$105.7838	$105.78	$105.80	$105.80
Purchase #4	$168.59	8.629%	$183.1376	$183.14	$183.15	$183.10
Purchase #5	$83.86	13.320%	$95.0302	$95.03	$95.05	$95.00
Purchase #6	$173.65	5.862%	$183.8294	$183.83	$183.85	$183.80
Purchase #7	$72.87	6.399%	$77.533	$77.53	$77.55	$77.50
7 purchase totals =	$806.30		$868.7350	$868.73	$868.80	$868.60