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	$10.33	3.772%	$10.7196	$10.72	$10.70	$10.70
Purchase #2	$240.89	9.169%	$262.9772	$262.98	$263.00	$263.00
Purchase #3	$204.96	8.399%	$222.1746	$222.17	$222.15	$222.20
Purchase #4	$91.97	8.123%	$99.4407	$99.44	$99.45	$99.40
Purchase #5	$167.90	4.294%	$175.1096	$175.11	$175.10	$175.10
Purchase #6	$139.69	9.781%	$153.3531	$153.35	$153.35	$153.40
Purchase #7	$134.66	12.626%	$151.6622	$151.66	$151.65	$151.70
7 purchase totals =	$990.40		$1,075.4370	$1,075.43	$1,075.40	$1,075.50