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	$11.27	9.842%	$12.3792	$12.38	$12.40	$12.40
Purchase #2	$57.59	9.299%	$62.9453	$62.95	$62.95	$62.90
Purchase #3	$248.76	12.523%	$279.9122	$279.91	$279.90	$279.90
Purchase #4	$190.61	9.866%	$209.4156	$209.42	$209.40	$209.40
Purchase #5	$37.32	3.136%	$38.4904	$38.49	$38.50	$38.50
Purchase #6	$225.60	6.204%	$239.5962	$239.60	$239.60	$239.60
Purchase #7	$198.43	6.485%	$211.2982	$211.30	$211.30	$211.30
7 purchase totals =	$969.58		$1,054.0371	$1,054.05	$1,054.05	$1,054.00