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	$27.36	7.637%	$29.4495	$29.45	$29.45	$29.40
Purchase #2	$53.44	3.476%	$55.2976	$55.30	$55.30	$55.30
Purchase #3	$18.26	11.528%	$20.365	$20.37	$20.35	$20.40
Purchase #4	$193.79	10.364%	$213.8744	$213.87	$213.85	$213.90
Purchase #5	$126.59	13.209%	$143.3113	$143.31	$143.30	$143.30
Purchase #6	$204.57	5.393%	$215.6025	$215.60	$215.60	$215.60
Purchase #7	$50.34	10.434%	$55.5925	$55.59	$55.60	$55.60
7 purchase totals =	$674.35		$733.4928	$733.49	$733.45	$733.50