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	$175.26	6.115%	$185.9771	$185.98	$186.00	$186.00
Purchase #2	$138.39	10.149%	$152.4352	$152.44	$152.45	$152.40
Purchase #3	$24.52	4.548%	$25.6352	$25.64	$25.65	$25.60
Purchase #4	$10.98	6.772%	$11.7236	$11.72	$11.70	$11.70
Purchase #5	$41.91	3.407%	$43.3379	$43.34	$43.35	$43.30
Purchase #6	$170.71	12.171%	$191.4871	$191.49	$191.50	$191.50
Purchase #7	$108.33	13.642%	$123.1084	$123.11	$123.10	$123.10
7 purchase totals =	$670.10		$733.7045	$733.72	$733.75	$733.60