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	$218.78	4.601%	$228.8461	$228.85	$228.85	$228.80
Purchase #2	$146.30	11.135%	$162.5905	$162.59	$162.60	$162.60
Purchase #3	$62.28	13.705%	$70.8155	$70.82	$70.80	$70.80
Purchase #4	$209.66	5.254%	$220.6755	$220.68	$220.70	$220.70
Purchase #5	$131.58	10.325%	$145.1656	$145.17	$145.15	$145.20
Purchase #6	$173.41	13.560%	$196.9244	$196.92	$196.90	$196.90
Purchase #7	$162.32	8.320%	$175.825	$175.83	$175.85	$175.80
7 purchase totals =	$1,104.33		$1,200.8426	$1,200.86	$1,200.85	$1,200.80