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	$84.61	11.736%	$94.5398	$94.54	$94.55	$94.50
Purchase #2	$117.72	8.424%	$127.6367	$127.64	$127.65	$127.60
Purchase #3	$49.51	6.520%	$52.7381	$52.74	$52.75	$52.70
Purchase #4	$45.42	7.285%	$48.7288	$48.73	$48.75	$48.70
Purchase #5	$103.45	7.679%	$111.3939	$111.39	$111.40	$111.40
Purchase #6	$224.48	9.725%	$246.3107	$246.31	$246.30	$246.30
Purchase #7	$62.93	4.787%	$65.9425	$65.94	$65.95	$65.90
7 purchase totals =	$688.12		$747.2905	$747.29	$747.35	$747.10