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	$92.42	11.574%	$103.1167	$103.12	$103.10	$103.10
Purchase #2	$25.53	11.194%	$28.3878	$28.39	$28.40	$28.40
Purchase #3	$169.26	3.266%	$174.788	$174.79	$174.80	$174.80
Purchase #4	$50.78	5.667%	$53.6577	$53.66	$53.65	$53.70
Purchase #5	$168.75	13.522%	$191.5684	$191.57	$191.55	$191.60
Purchase #6	$205.40	7.854%	$221.5321	$221.53	$221.55	$221.50
Purchase #7	$239.38	3.103%	$246.808	$246.81	$246.80	$246.80
7 purchase totals =	$951.52		$1,019.8587	$1,019.87	$1,019.85	$1,019.90