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	$92.59	13.798%	$105.3656	$105.37	$105.35	$105.40
Purchase #2	$28.48	6.143%	$30.2295	$30.23	$30.25	$30.20
Purchase #3	$145.48	5.265%	$153.1395	$153.14	$153.15	$153.10
Purchase #4	$230.69	4.252%	$240.4989	$240.50	$240.50	$240.50
Purchase #5	$74.74	9.675%	$81.9711	$81.97	$81.95	$82.00
Purchase #6	$203.69	9.615%	$223.2748	$223.27	$223.25	$223.30
Purchase #7	$228.33	11.837%	$255.3574	$255.36	$255.35	$255.40
7 purchase totals =	$1,004.00		$1,089.8368	$1,089.84	$1,089.80	$1,089.90