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	$123.66	3.361%	$127.8162	$127.82	$127.80	$127.80
Purchase #2	$209.96	7.766%	$226.2655	$226.27	$226.25	$226.30
Purchase #3	$59.49	13.209%	$67.348	$67.35	$67.35	$67.30
Purchase #4	$12.62	7.693%	$13.5909	$13.59	$13.60	$13.60
Purchase #5	$225.94	10.122%	$248.8096	$248.81	$248.80	$248.80
Purchase #6	$68.33	11.607%	$76.2611	$76.26	$76.25	$76.30
Purchase #7	$210.96	4.846%	$221.1831	$221.18	$221.20	$221.20
7 purchase totals =	$910.96		$981.2744	$981.28	$981.25	$981.30