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	$54.89	8.832%	$59.7379	$59.74	$59.75	$59.70
Purchase #2	$150.99	7.681%	$162.5875	$162.59	$162.60	$162.60
Purchase #3	$196.45	7.547%	$211.2761	$211.28	$211.30	$211.30
Purchase #4	$118.25	13.682%	$134.429	$134.43	$134.45	$134.40
Purchase #5	$223.49	12.670%	$251.8062	$251.81	$251.80	$251.80
Purchase #6	$151.98	13.718%	$172.8286	$172.83	$172.85	$172.80
Purchase #7	$188.34	3.142%	$194.2576	$194.26	$194.25	$194.30
7 purchase totals =	$1,084.39		$1,186.9229	$1,186.94	$1,187.00	$1,186.90