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	$40.65	9.619%	$44.5601	$44.56	$44.55	$44.60
Purchase #2	$133.95	13.624%	$152.1993	$152.20	$152.20	$152.20
Purchase #3	$199.38	7.567%	$214.4671	$214.47	$214.45	$214.50
Purchase #4	$83.92	11.423%	$93.5062	$93.51	$93.50	$93.50
Purchase #5	$195.32	4.592%	$204.2891	$204.29	$204.30	$204.30
Purchase #6	$55.44	7.518%	$59.608	$59.61	$59.60	$59.60
Purchase #7	$123.89	7.553%	$133.2474	$133.25	$133.25	$133.20
7 purchase totals =	$832.55		$901.8772	$901.89	$901.85	$901.90