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	$198.76	3.111%	$204.9434	$204.94	$204.95	$204.90
Purchase #2	$205.46	11.263%	$228.601	$228.60	$228.60	$228.60
Purchase #3	$32.65	10.456%	$36.0639	$36.06	$36.05	$36.10
Purchase #4	$64.30	10.357%	$70.9596	$70.96	$70.95	$71.00
Purchase #5	$52.32	6.218%	$55.5733	$55.57	$55.55	$55.60
Purchase #6	$137.68	10.301%	$151.8624	$151.86	$151.85	$151.90
Purchase #7	$85.35	7.199%	$91.4943	$91.49	$91.50	$91.50
7 purchase totals =	$776.52		$839.4979	$839.48	$839.45	$839.60