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	$150.29	8.144%	$162.5296	$162.53	$162.55	$162.50
Purchase #2	$127.49	5.806%	$134.8921	$134.89	$134.90	$134.90
Purchase #3	$207.35	7.833%	$223.5917	$223.59	$223.60	$223.60
Purchase #4	$86.51	7.464%	$92.9671	$92.97	$92.95	$93.00
Purchase #5	$88.35	12.553%	$99.4406	$99.44	$99.45	$99.40
Purchase #6	$130.60	10.104%	$143.7958	$143.80	$143.80	$143.80
Purchase #7	$195.33	11.692%	$218.168	$218.17	$218.15	$218.20
7 purchase totals =	$985.92		$1,075.3849	$1,075.39	$1,075.40	$1,075.40