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	$69.48	10.508%	$76.781	$76.78	$76.80	$76.80
Purchase #2	$46.75	5.865%	$49.4919	$49.49	$49.50	$49.50
Purchase #3	$49.70	8.314%	$53.8321	$53.83	$53.85	$53.80
Purchase #4	$67.52	8.488%	$73.2511	$73.25	$73.25	$73.30
Purchase #5	$52.28	13.331%	$59.2494	$59.25	$59.25	$59.20
Purchase #6	$51.69	7.793%	$55.7182	$55.72	$55.70	$55.70
Purchase #7	$235.87	9.663%	$258.6621	$258.66	$258.65	$258.70
7 purchase totals =	$573.29		$626.9858	$626.98	$627.00	$627.00