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	$187.28	11.658%	$209.1131	$209.11	$209.10	$209.10
Purchase #2	$74.65	5.659%	$78.8744	$78.87	$78.85	$78.90
Purchase #3	$76.37	4.190%	$79.5699	$79.57	$79.55	$79.60
Purchase #4	$34.88	10.254%	$38.4566	$38.46	$38.45	$38.50
Purchase #5	$236.85	13.740%	$269.3932	$269.39	$269.40	$269.40
Purchase #6	$45.45	5.849%	$48.1084	$48.11	$48.10	$48.10
Purchase #7	$162.76	13.425%	$184.6105	$184.61	$184.60	$184.60
7 purchase totals =	$818.24		$908.1261	$908.12	$908.05	$908.20