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	$107.64	4.681%	$112.6786	$112.68	$112.70	$112.70
Purchase #2	$75.88	12.141%	$85.0926	$85.09	$85.10	$85.10
Purchase #3	$185.84	6.842%	$198.5552	$198.56	$198.55	$198.60
Purchase #4	$153.51	9.746%	$168.4711	$168.47	$168.45	$168.50
Purchase #5	$83.63	9.617%	$91.6727	$91.67	$91.65	$91.70
Purchase #6	$22.78	6.565%	$24.2755	$24.28	$24.30	$24.30
Purchase #7	$183.25	7.350%	$196.7189	$196.72	$196.70	$196.70
7 purchase totals =	$812.53		$877.4646	$877.47	$877.45	$877.60