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	$122.47	9.804%	$134.477	$134.48	$134.50	$134.50
Purchase #2	$144.84	4.856%	$151.8734	$151.87	$151.85	$151.90
Purchase #3	$146.57	7.517%	$157.5877	$157.59	$157.60	$157.60
Purchase #4	$24.41	13.120%	$27.6126	$27.61	$27.60	$27.60
Purchase #5	$214.62	12.165%	$240.7285	$240.73	$240.75	$240.70
Purchase #6	$127.82	13.307%	$144.829	$144.83	$144.85	$144.80
Purchase #7	$56.74	4.654%	$59.3807	$59.38	$59.40	$59.40
7 purchase totals =	$837.47		$916.4889	$916.49	$916.55	$916.50