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	$160.89	7.540%	$173.0211	$173.02	$173.00	$173.00
Purchase #2	$140.62	8.556%	$152.6514	$152.65	$152.65	$152.70
Purchase #3	$28.43	10.776%	$31.4936	$31.49	$31.50	$31.50
Purchase #4	$30.97	4.653%	$32.411	$32.41	$32.40	$32.40
Purchase #5	$78.36	13.689%	$89.0867	$89.09	$89.10	$89.10
Purchase #6	$62.50	10.491%	$69.0569	$69.06	$69.05	$69.10
Purchase #7	$58.62	7.146%	$62.809	$62.81	$62.80	$62.80
7 purchase totals =	$560.39		$610.5297	$610.53	$610.50	$610.60