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	$237.45	7.343%	$254.886	$254.89	$254.90	$254.90
Purchase #2	$240.25	9.604%	$263.3236	$263.32	$263.30	$263.30
Purchase #3	$37.73	4.653%	$39.4856	$39.49	$39.50	$39.50
Purchase #4	$62.74	9.601%	$68.7637	$68.76	$68.75	$68.80
Purchase #5	$105.32	9.595%	$115.4255	$115.43	$115.45	$115.40
Purchase #6	$10.77	12.546%	$12.1212	$12.12	$12.10	$12.10
Purchase #7	$30.92	6.399%	$32.8986	$32.90	$32.90	$32.90
7 purchase totals =	$725.18		$786.9042	$786.91	$786.90	$786.90