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	$217.27	5.814%	$229.9021	$229.90	$229.90	$229.90
Purchase #2	$163.58	4.763%	$171.3713	$171.37	$171.35	$171.40
Purchase #3	$30.73	12.126%	$34.4563	$34.46	$34.45	$34.50
Purchase #4	$18.41	11.661%	$20.5568	$20.56	$20.55	$20.60
Purchase #5	$137.94	12.409%	$155.057	$155.06	$155.05	$155.10
Purchase #6	$156.28	10.639%	$172.9066	$172.91	$172.90	$172.90
Purchase #7	$178.73	5.164%	$187.9596	$187.96	$187.95	$188.00
7 purchase totals =	$902.94		$972.2097	$972.22	$972.15	$972.40