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	$183.26	9.378%	$200.4461	$200.45	$200.45	$200.40
Purchase #2	$106.73	7.185%	$114.3986	$114.40	$114.40	$114.40
Purchase #3	$123.98	9.745%	$136.0619	$136.06	$136.05	$136.10
Purchase #4	$178.91	3.729%	$185.5816	$185.58	$185.60	$185.60
Purchase #5	$46.68	11.560%	$52.0762	$52.08	$52.10	$52.10
Purchase #6	$250.78	11.573%	$279.8028	$279.80	$279.80	$279.80
Purchase #7	$134.78	6.215%	$143.1566	$143.16	$143.15	$143.20
7 purchase totals =	$1,025.12		$1,111.5238	$1,111.53	$1,111.55	$1,111.60