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	$9.67	13.328%	$10.9588	$10.96	$10.95	$11.00
Purchase #2	$153.56	11.377%	$171.0305	$171.03	$171.05	$171.00
Purchase #3	$133.73	6.522%	$142.4519	$142.45	$142.45	$142.50
Purchase #4	$75.72	12.627%	$85.2812	$85.28	$85.30	$85.30
Purchase #5	$143.68	7.772%	$154.8468	$154.85	$154.85	$154.80
Purchase #6	$38.73	9.657%	$42.4702	$42.47	$42.45	$42.50
Purchase #7	$219.32	4.731%	$229.696	$229.70	$229.70	$229.70
7 purchase totals =	$774.41		$836.7354	$836.74	$836.75	$836.80