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	$33.89	13.431%	$38.4418	$38.44	$38.45	$38.40
Purchase #2	$130.59	12.184%	$146.5011	$146.50	$146.50	$146.50
Purchase #3	$115.35	7.359%	$123.8386	$123.84	$123.85	$123.80
Purchase #4	$226.49	4.779%	$237.314	$237.31	$237.30	$237.30
Purchase #5	$89.60	4.621%	$93.7404	$93.74	$93.75	$93.70
Purchase #6	$96.93	12.722%	$109.2614	$109.26	$109.25	$109.30
Purchase #7	$95.54	10.499%	$105.5707	$105.57	$105.55	$105.60
7 purchase totals =	$788.39		$854.6680	$854.66	$854.65	$854.60