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	$239.84	3.280%	$247.7068	$247.71	$247.70	$247.70
Purchase #2	$39.33	9.477%	$43.0573	$43.06	$43.05	$43.10
Purchase #3	$89.79	11.468%	$100.0871	$100.09	$100.10	$100.10
Purchase #4	$9.98	10.500%	$11.0279	$11.03	$11.05	$11.00
Purchase #5	$178.66	4.458%	$186.6247	$186.62	$186.60	$186.60
Purchase #6	$135.89	10.763%	$150.5158	$150.52	$150.50	$150.50
Purchase #7	$26.67	6.680%	$28.4516	$28.45	$28.45	$28.50
7 purchase totals =	$720.16		$767.4712	$767.48	$767.45	$767.50