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	$161.88	10.800%	$179.363	$179.36	$179.35	$179.40
Purchase #2	$87.63	9.314%	$95.7919	$95.79	$95.80	$95.80
Purchase #3	$101.83	3.347%	$105.2383	$105.24	$105.25	$105.20
Purchase #4	$213.52	3.245%	$220.4487	$220.45	$220.45	$220.40
Purchase #5	$86.79	3.339%	$89.6879	$89.69	$89.70	$89.70
Purchase #6	$29.47	10.739%	$32.6348	$32.63	$32.65	$32.60
Purchase #7	$32.77	13.690%	$37.2562	$37.26	$37.25	$37.30
7 purchase totals =	$713.89		$760.4208	$760.42	$760.45	$760.40