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	$148.62	12.768%	$167.5958	$167.60	$167.60	$167.60
Purchase #2	$220.93	13.759%	$251.3278	$251.33	$251.35	$251.30
Purchase #3	$248.35	11.369%	$276.5849	$276.58	$276.60	$276.60
Purchase #4	$99.46	11.846%	$111.242	$111.24	$111.25	$111.20
Purchase #5	$26.90	7.152%	$28.8239	$28.82	$28.80	$28.80
Purchase #6	$43.86	11.294%	$48.8135	$48.81	$48.80	$48.80
Purchase #7	$183.32	3.256%	$189.2889	$189.29	$189.30	$189.30
7 purchase totals =	$971.44		$1,073.6768	$1,073.67	$1,073.70	$1,073.60