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	$43.52	7.694%	$46.8684	$46.87	$46.85	$46.90
Purchase #2	$55.46	7.154%	$59.4276	$59.43	$59.45	$59.40
Purchase #3	$18.28	9.543%	$20.0245	$20.02	$20.00	$20.00
Purchase #4	$68.86	12.711%	$77.6128	$77.61	$77.60	$77.60
Purchase #5	$173.39	8.212%	$187.6288	$187.63	$187.65	$187.60
Purchase #6	$243.94	12.610%	$274.7008	$274.70	$274.70	$274.70
Purchase #7	$224.30	10.427%	$247.6878	$247.69	$247.70	$247.70
7 purchase totals =	$827.75		$913.9507	$913.95	$913.95	$913.90