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	$76.69	11.560%	$85.5554	$85.56	$85.55	$85.60
Purchase #2	$114.86	11.105%	$127.6152	$127.62	$127.60	$127.60
Purchase #3	$30.47	6.320%	$32.3957	$32.40	$32.40	$32.40
Purchase #4	$190.53	7.682%	$205.1665	$205.17	$205.15	$205.20
Purchase #5	$89.35	3.627%	$92.5907	$92.59	$92.60	$92.60
Purchase #6	$175.68	10.372%	$193.9015	$193.90	$193.90	$193.90
Purchase #7	$222.45	10.442%	$245.6782	$245.68	$245.70	$245.70
7 purchase totals =	$900.03		$982.9032	$982.92	$982.90	$983.00