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	$150.70	11.297%	$167.7246	$167.72	$167.70	$167.70
Purchase #2	$83.74	12.335%	$94.0693	$94.07	$94.05	$94.10
Purchase #3	$244.64	6.366%	$260.2138	$260.21	$260.20	$260.20
Purchase #4	$169.27	12.777%	$190.8976	$190.90	$190.90	$190.90
Purchase #5	$238.93	6.786%	$255.1438	$255.14	$255.15	$255.10
Purchase #6	$49.60	7.719%	$53.4286	$53.43	$53.45	$53.40
Purchase #7	$67.99	6.399%	$72.3407	$72.34	$72.35	$72.30
7 purchase totals =	$1,004.87		$1,093.8184	$1,093.81	$1,093.80	$1,093.70