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	$160.86	4.364%	$167.8799	$167.88	$167.90	$167.90
Purchase #2	$210.69	7.116%	$225.6827	$225.68	$225.70	$225.70
Purchase #3	$68.57	5.820%	$72.5608	$72.56	$72.55	$72.60
Purchase #4	$180.37	4.513%	$188.5101	$188.51	$188.50	$188.50
Purchase #5	$75.38	9.470%	$82.5185	$82.52	$82.50	$82.50
Purchase #6	$29.67	9.154%	$32.386	$32.39	$32.40	$32.40
Purchase #7	$193.81	7.170%	$207.7062	$207.71	$207.70	$207.70
7 purchase totals =	$919.35		$977.2442	$977.25	$977.25	$977.30