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	$174.69	12.670%	$196.8232	$196.82	$196.80	$196.80
Purchase #2	$249.47	13.140%	$282.2504	$282.25	$282.25	$282.30
Purchase #3	$9.45	4.823%	$9.9058	$9.91	$9.90	$9.90
Purchase #4	$239.72	3.831%	$248.9037	$248.90	$248.90	$248.90
Purchase #5	$14.71	13.866%	$16.7497	$16.75	$16.75	$16.70
Purchase #6	$55.52	3.465%	$57.4438	$57.44	$57.45	$57.40
Purchase #7	$28.86	13.735%	$32.8239	$32.82	$32.80	$32.80
7 purchase totals =	$772.42		$844.9005	$844.89	$844.85	$844.80