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	$148.62	12.832%	$167.6909	$167.69	$167.70	$167.70
Purchase #2	$153.96	5.689%	$162.7188	$162.72	$162.70	$162.70
Purchase #3	$162.37	7.314%	$174.2457	$174.25	$174.25	$174.20
Purchase #4	$6.42	13.190%	$7.2668	$7.27	$7.25	$7.30
Purchase #5	$38.52	6.833%	$41.1521	$41.15	$41.15	$41.20
Purchase #6	$122.87	4.675%	$128.6142	$128.61	$128.60	$128.60
Purchase #7	$144.61	11.155%	$160.7412	$160.74	$160.75	$160.70
7 purchase totals =	$777.37		$842.4297	$842.43	$842.40	$842.40