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	$131.85	13.641%	$149.8357	$149.84	$149.85	$149.80
Purchase #2	$29.94	10.584%	$33.1088	$33.11	$33.10	$33.10
Purchase #3	$65.30	11.244%	$72.6423	$72.64	$72.65	$72.60
Purchase #4	$45.69	8.654%	$49.644	$49.64	$49.65	$49.60
Purchase #5	$97.42	10.545%	$107.6929	$107.69	$107.70	$107.70
Purchase #6	$34.48	13.456%	$39.1196	$39.12	$39.10	$39.10
Purchase #7	$103.69	5.589%	$109.4852	$109.49	$109.50	$109.50
7 purchase totals =	$508.37		$561.5285	$561.53	$561.55	$561.40