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	$170.25	5.109%	$178.9481	$178.95	$178.95	$178.90
Purchase #2	$61.29	9.217%	$66.9391	$66.94	$66.95	$66.90
Purchase #3	$173.47	10.451%	$191.5993	$191.60	$191.60	$191.60
Purchase #4	$175.85	10.478%	$194.2756	$194.28	$194.30	$194.30
Purchase #5	$68.50	4.726%	$71.7373	$71.74	$71.75	$71.70
Purchase #6	$236.35	7.587%	$254.2819	$254.28	$254.30	$254.30
Purchase #7	$114.37	11.675%	$127.7227	$127.72	$127.70	$127.70
7 purchase totals =	$1,000.08		$1,085.5040	$1,085.51	$1,085.55	$1,085.40