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	$66.79	9.162%	$72.9093	$72.91	$72.90	$72.90
Purchase #2	$176.75	7.674%	$190.3138	$190.31	$190.30	$190.30
Purchase #3	$42.41	3.530%	$43.9071	$43.91	$43.90	$43.90
Purchase #4	$82.48	4.149%	$85.9021	$85.90	$85.90	$85.90
Purchase #5	$224.76	13.762%	$255.6915	$255.69	$255.70	$255.70
Purchase #6	$167.28	8.624%	$181.7062	$181.71	$181.70	$181.70
Purchase #7	$41.32	6.624%	$44.057	$44.06	$44.05	$44.10
7 purchase totals =	$801.79		$874.4870	$874.49	$874.45	$874.50