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	$200.75	12.713%	$226.2713	$226.27	$226.25	$226.30
Purchase #2	$78.25	9.653%	$85.8035	$85.80	$85.80	$85.80
Purchase #3	$106.55	4.593%	$111.4438	$111.44	$111.45	$111.40
Purchase #4	$126.60	13.618%	$143.8404	$143.84	$143.85	$143.80
Purchase #5	$141.32	6.233%	$150.1285	$150.13	$150.15	$150.10
Purchase #6	$75.44	5.334%	$79.464	$79.46	$79.45	$79.50
Purchase #7	$245.65	4.440%	$256.5569	$256.56	$256.55	$256.60
7 purchase totals =	$974.56		$1,053.5084	$1,053.50	$1,053.50	$1,053.50