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	$64.95	11.725%	$72.5654	$72.57	$72.55	$72.60
Purchase #2	$136.28	5.592%	$143.9008	$143.90	$143.90	$143.90
Purchase #3	$120.42	11.498%	$134.2659	$134.27	$134.25	$134.30
Purchase #4	$7.86	4.228%	$8.1923	$8.19	$8.20	$8.20
Purchase #5	$142.30	9.774%	$156.2084	$156.21	$156.20	$156.20
Purchase #6	$148.52	6.672%	$158.4293	$158.43	$158.45	$158.40
Purchase #7	$99.45	10.212%	$109.6058	$109.61	$109.60	$109.60
7 purchase totals =	$719.78		$783.1679	$783.18	$783.15	$783.20