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	$249.37	5.860%	$263.9831	$263.98	$264.00	$264.00
Purchase #2	$96.34	9.732%	$105.7158	$105.72	$105.70	$105.70
Purchase #3	$32.68	4.822%	$34.2558	$34.26	$34.25	$34.30
Purchase #4	$142.99	9.428%	$156.4711	$156.47	$156.45	$156.50
Purchase #5	$152.61	13.472%	$173.1696	$173.17	$173.15	$173.20
Purchase #6	$220.99	7.720%	$238.0504	$238.05	$238.05	$238.10
Purchase #7	$42.47	5.756%	$44.9146	$44.91	$44.90	$44.90
7 purchase totals =	$937.45		$1,016.5604	$1,016.56	$1,016.50	$1,016.70