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	$167.54	4.795%	$175.5735	$175.57	$175.55	$175.60
Purchase #2	$121.60	8.784%	$132.2813	$132.28	$132.30	$132.30
Purchase #3	$235.82	6.241%	$250.5375	$250.54	$250.55	$250.50
Purchase #4	$133.64	7.477%	$143.6323	$143.63	$143.65	$143.60
Purchase #5	$38.41	11.495%	$42.8252	$42.83	$42.85	$42.80
Purchase #6	$72.78	8.653%	$79.0777	$79.08	$79.10	$79.10
Purchase #7	$45.57	11.116%	$50.6356	$50.64	$50.65	$50.60
7 purchase totals =	$815.36		$874.5631	$874.57	$874.65	$874.50