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	$108.33	13.627%	$123.0921	$123.09	$123.10	$123.10
Purchase #2	$159.77	9.478%	$174.913	$174.91	$174.90	$174.90
Purchase #3	$193.91	13.366%	$219.828	$219.83	$219.85	$219.80
Purchase #4	$63.36	13.245%	$71.752	$71.75	$71.75	$71.80
Purchase #5	$170.72	11.578%	$190.486	$190.49	$190.50	$190.50
Purchase #6	$135.38	7.562%	$145.6174	$145.62	$145.60	$145.60
Purchase #7	$66.28	10.631%	$73.3262	$73.33	$73.35	$73.30
7 purchase totals =	$897.75		$999.0147	$999.02	$999.05	$999.00