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	$219.46	9.488%	$240.2824	$240.28	$240.30	$240.30
Purchase #2	$36.70	7.287%	$39.3743	$39.37	$39.35	$39.40
Purchase #3	$190.28	10.821%	$210.8702	$210.87	$210.85	$210.90
Purchase #4	$208.76	7.687%	$224.8074	$224.81	$224.80	$224.80
Purchase #5	$77.81	7.468%	$83.6209	$83.62	$83.60	$83.60
Purchase #6	$101.32	9.812%	$111.2615	$111.26	$111.25	$111.30
Purchase #7	$219.68	9.659%	$240.8989	$240.90	$240.90	$240.90
7 purchase totals =	$1,054.01		$1,151.1156	$1,151.11	$1,151.05	$1,151.20