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	$183.97	11.640%	$205.3841	$205.38	$205.40	$205.40
Purchase #2	$37.86	13.359%	$42.9177	$42.92	$42.90	$42.90
Purchase #3	$134.39	11.581%	$149.9537	$149.95	$149.95	$150.00
Purchase #4	$151.59	11.110%	$168.4316	$168.43	$168.45	$168.40
Purchase #5	$236.31	7.701%	$254.5082	$254.51	$254.50	$254.50
Purchase #6	$125.87	5.571%	$132.8822	$132.88	$132.90	$132.90
Purchase #7	$13.39	8.215%	$14.49	$14.49	$14.50	$14.50
7 purchase totals =	$883.38		$968.5675	$968.56	$968.60	$968.60