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	$89.48	13.681%	$101.7218	$101.72	$101.70	$101.70
Purchase #2	$185.41	6.698%	$197.8288	$197.83	$197.85	$197.80
Purchase #3	$220.26	9.252%	$240.6385	$240.64	$240.65	$240.60
Purchase #4	$163.49	13.463%	$185.5007	$185.50	$185.50	$185.50
Purchase #5	$128.49	10.861%	$142.4453	$142.45	$142.45	$142.40
Purchase #6	$40.90	13.442%	$46.3978	$46.40	$46.40	$46.40
Purchase #7	$228.28	10.858%	$253.0666	$253.07	$253.05	$253.10
7 purchase totals =	$1,056.31		$1,167.5995	$1,167.61	$1,167.60	$1,167.50