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	$150.60	10.292%	$166.0998	$166.10	$166.10	$166.10
Purchase #2	$142.76	5.131%	$150.085	$150.09	$150.10	$150.10
Purchase #3	$188.70	3.456%	$195.2215	$195.22	$195.20	$195.20
Purchase #4	$72.51	10.413%	$80.0605	$80.06	$80.05	$80.10
Purchase #5	$226.56	12.770%	$255.4917	$255.49	$255.50	$255.50
Purchase #6	$142.36	10.196%	$156.875	$156.88	$156.90	$156.90
Purchase #7	$230.64	11.133%	$256.3172	$256.32	$256.30	$256.30
7 purchase totals =	$1,154.13		$1,260.1507	$1,260.16	$1,260.15	$1,260.20