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	$61.50	12.544%	$69.2146	$69.21	$69.20	$69.20
Purchase #2	$107.77	4.226%	$112.3244	$112.32	$112.30	$112.30
Purchase #3	$59.69	12.706%	$67.2742	$67.27	$67.25	$67.30
Purchase #4	$95.59	11.874%	$106.9404	$106.94	$106.95	$106.90
Purchase #5	$217.28	9.752%	$238.4691	$238.47	$238.45	$238.50
Purchase #6	$125.65	4.675%	$131.5241	$131.52	$131.50	$131.50
Purchase #7	$150.52	5.431%	$158.6947	$158.69	$158.70	$158.70
7 purchase totals =	$818.00		$884.4415	$884.42	$884.35	$884.40