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	$88.86	11.485%	$99.0656	$99.07	$99.05	$99.10
Purchase #2	$64.35	13.305%	$72.9118	$72.91	$72.90	$72.90
Purchase #3	$104.51	13.489%	$118.6074	$118.61	$118.60	$118.60
Purchase #4	$216.96	4.338%	$226.3717	$226.37	$226.35	$226.40
Purchase #5	$114.59	11.814%	$128.1277	$128.13	$128.15	$128.10
Purchase #6	$137.98	10.749%	$152.8115	$152.81	$152.80	$152.80
Purchase #7	$151.65	8.318%	$164.2642	$164.26	$164.25	$164.30
7 purchase totals =	$878.90		$962.1599	$962.16	$962.10	$962.20