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	$73.53	7.338%	$78.9256	$78.93	$78.95	$78.90
Purchase #2	$75.68	8.434%	$82.0629	$82.06	$82.05	$82.10
Purchase #3	$157.33	6.420%	$167.4306	$167.43	$167.45	$167.40
Purchase #4	$223.40	4.262%	$232.9213	$232.92	$232.90	$232.90
Purchase #5	$192.75	4.175%	$200.7973	$200.80	$200.80	$200.80
Purchase #6	$54.30	13.208%	$61.4719	$61.47	$61.45	$61.50
Purchase #7	$100.91	11.697%	$112.7134	$112.71	$112.70	$112.70
7 purchase totals =	$877.90		$936.3230	$936.32	$936.30	$936.30