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	$130.64	9.568%	$143.1396	$143.14	$143.15	$143.10
Purchase #2	$240.93	10.299%	$265.7434	$265.74	$265.75	$265.70
Purchase #3	$167.36	6.729%	$178.6217	$178.62	$178.60	$178.60
Purchase #4	$213.93	4.637%	$223.8499	$223.85	$223.85	$223.80
Purchase #5	$28.59	12.623%	$32.1989	$32.20	$32.20	$32.20
Purchase #6	$54.77	13.535%	$62.1831	$62.18	$62.20	$62.20
Purchase #7	$181.35	10.516%	$200.4208	$200.42	$200.40	$200.40
7 purchase totals =	$1,017.57		$1,106.1574	$1,106.15	$1,106.15	$1,106.00