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	$168.84	11.866%	$188.8746	$188.87	$188.85	$188.90
Purchase #2	$176.62	6.659%	$188.3811	$188.38	$188.40	$188.40
Purchase #3	$248.28	4.499%	$259.4501	$259.45	$259.45	$259.50
Purchase #4	$123.65	11.487%	$137.8537	$137.85	$137.85	$137.90
Purchase #5	$139.82	4.808%	$146.5425	$146.54	$146.55	$146.50
Purchase #6	$11.48	8.653%	$12.4734	$12.47	$12.45	$12.50
Purchase #7	$222.39	6.861%	$237.6482	$237.65	$237.65	$237.60
7 purchase totals =	$1,091.08		$1,171.2236	$1,171.21	$1,171.20	$1,171.30