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	$148.92	5.322%	$156.8455	$156.85	$156.85	$156.80
Purchase #2	$249.97	5.203%	$262.9759	$262.98	$263.00	$263.00
Purchase #3	$48.85	13.472%	$55.4311	$55.43	$55.45	$55.40
Purchase #4	$46.98	7.697%	$50.5961	$50.60	$50.60	$50.60
Purchase #5	$64.27	10.821%	$71.2247	$71.22	$71.20	$71.20
Purchase #6	$37.76	13.396%	$42.8183	$42.82	$42.80	$42.80
Purchase #7	$200.78	13.676%	$228.2387	$228.24	$228.25	$228.20
7 purchase totals =	$797.53		$868.1303	$868.14	$868.15	$868.00