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	$83.94	11.668%	$93.7341	$93.73	$93.75	$93.70
Purchase #2	$250.37	7.605%	$269.4106	$269.41	$269.40	$269.40
Purchase #3	$74.91	4.627%	$78.3761	$78.38	$78.40	$78.40
Purchase #4	$69.92	12.794%	$78.8656	$78.87	$78.85	$78.90
Purchase #5	$111.26	5.240%	$117.09	$117.09	$117.10	$117.10
Purchase #6	$205.45	8.462%	$222.8352	$222.84	$222.85	$222.80
Purchase #7	$22.40	7.577%	$24.0972	$24.10	$24.10	$24.10
7 purchase totals =	$818.25		$884.4088	$884.42	$884.45	$884.40