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	$130.54	8.515%	$141.6555	$141.66	$141.65	$141.70
Purchase #2	$245.40	4.657%	$256.8283	$256.83	$256.85	$256.80
Purchase #3	$235.28	6.671%	$250.9755	$250.98	$251.00	$251.00
Purchase #4	$175.94	5.810%	$186.1621	$186.16	$186.15	$186.20
Purchase #5	$150.91	4.703%	$158.0073	$158.01	$158.00	$158.00
Purchase #6	$112.83	13.816%	$128.4186	$128.42	$128.40	$128.40
Purchase #7	$37.81	12.487%	$42.5313	$42.53	$42.55	$42.50
7 purchase totals =	$1,088.71		$1,164.5786	$1,164.59	$1,164.60	$1,164.60