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	$225.56	7.697%	$242.9214	$242.92	$242.90	$242.90
Purchase #2	$234.75	12.662%	$264.474	$264.47	$264.45	$264.50
Purchase #3	$85.33	11.852%	$95.4433	$95.44	$95.45	$95.40
Purchase #4	$36.76	13.562%	$41.7454	$41.75	$41.75	$41.70
Purchase #5	$132.40	10.734%	$146.6118	$146.61	$146.60	$146.60
Purchase #6	$98.44	5.472%	$103.8266	$103.83	$103.85	$103.80
Purchase #7	$59.74	8.554%	$64.8502	$64.85	$64.85	$64.90
7 purchase totals =	$872.98		$959.8727	$959.87	$959.85	$959.80