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	$68.75	13.168%	$77.803	$77.80	$77.80	$77.80
Purchase #2	$142.39	11.245%	$158.4018	$158.40	$158.40	$158.40
Purchase #3	$219.28	13.677%	$249.2709	$249.27	$249.25	$249.30
Purchase #4	$50.31	13.117%	$56.9092	$56.91	$56.90	$56.90
Purchase #5	$71.76	6.826%	$76.6583	$76.66	$76.65	$76.70
Purchase #6	$217.33	3.665%	$225.2951	$225.30	$225.30	$225.30
Purchase #7	$195.43	11.850%	$218.5885	$218.59	$218.60	$218.60
7 purchase totals =	$965.25		$1,062.9268	$1,062.93	$1,062.90	$1,063.00