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	$175.36	7.676%	$188.8206	$188.82	$188.80	$188.80
Purchase #2	$72.53	5.385%	$76.4357	$76.44	$76.45	$76.40
Purchase #3	$32.77	4.852%	$34.36	$34.36	$34.35	$34.40
Purchase #4	$55.91	6.159%	$59.3535	$59.35	$59.35	$59.40
Purchase #5	$188.52	4.117%	$196.2814	$196.28	$196.30	$196.30
Purchase #6	$54.57	11.552%	$60.8739	$60.87	$60.85	$60.90
Purchase #7	$104.71	3.720%	$108.6052	$108.61	$108.60	$108.60
7 purchase totals =	$684.37		$724.7303	$724.73	$724.70	$724.80