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	$214.55	11.219%	$238.6204	$238.62	$238.60	$238.60
Purchase #2	$19.31	6.614%	$20.5872	$20.59	$20.60	$20.60
Purchase #3	$105.94	8.131%	$114.554	$114.55	$114.55	$114.60
Purchase #4	$209.80	9.533%	$229.8002	$229.80	$229.80	$229.80
Purchase #5	$210.39	9.522%	$230.4233	$230.42	$230.40	$230.40
Purchase #6	$135.89	7.826%	$146.5248	$146.52	$146.50	$146.50
Purchase #7	$81.40	5.661%	$86.0081	$86.01	$86.00	$86.00
7 purchase totals =	$977.28		$1,066.5180	$1,066.51	$1,066.45	$1,066.50