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	$210.67	11.816%	$235.5628	$235.56	$235.55	$235.60
Purchase #2	$233.66	10.837%	$258.9817	$258.98	$259.00	$259.00
Purchase #3	$184.51	3.465%	$190.9033	$190.90	$190.90	$190.90
Purchase #4	$138.73	11.262%	$154.3538	$154.35	$154.35	$154.40
Purchase #5	$41.87	4.701%	$43.8383	$43.84	$43.85	$43.80
Purchase #6	$60.83	11.490%	$67.8194	$67.82	$67.80	$67.80
Purchase #7	$55.82	9.562%	$61.1575	$61.16	$61.15	$61.20
7 purchase totals =	$926.09		$1,012.6168	$1,012.61	$1,012.60	$1,012.70