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	$128.27	12.659%	$144.5077	$144.51	$144.50	$144.50
Purchase #2	$75.78	6.574%	$80.7618	$80.76	$80.75	$80.80
Purchase #3	$56.60	12.113%	$63.456	$63.46	$63.45	$63.50
Purchase #4	$217.30	5.791%	$229.8838	$229.88	$229.90	$229.90
Purchase #5	$212.39	8.159%	$229.7189	$229.72	$229.70	$229.70
Purchase #6	$190.72	8.541%	$207.0094	$207.01	$207.00	$207.00
Purchase #7	$168.27	13.401%	$190.8199	$190.82	$190.80	$190.80
7 purchase totals =	$1,049.33		$1,146.1575	$1,146.16	$1,146.10	$1,146.20