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	$197.60	8.709%	$214.809	$214.81	$214.80	$214.80
Purchase #2	$151.77	11.219%	$168.7971	$168.80	$168.80	$168.80
Purchase #3	$42.69	11.846%	$47.7471	$47.75	$47.75	$47.70
Purchase #4	$151.42	10.205%	$166.8724	$166.87	$166.85	$166.90
Purchase #5	$43.77	9.673%	$48.0039	$48.00	$48.00	$48.00
Purchase #6	$163.55	13.461%	$185.5655	$185.57	$185.55	$185.60
Purchase #7	$41.96	7.376%	$45.055	$45.06	$45.05	$45.10
7 purchase totals =	$792.76		$876.8500	$876.86	$876.80	$876.90