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	$124.52	6.618%	$132.7607	$132.76	$132.75	$132.80
Purchase #2	$63.82	13.610%	$72.5059	$72.51	$72.50	$72.50
Purchase #3	$158.88	4.729%	$166.3934	$166.39	$166.40	$166.40
Purchase #4	$171.79	7.834%	$185.248	$185.25	$185.25	$185.20
Purchase #5	$172.77	5.574%	$182.4002	$182.40	$182.40	$182.40
Purchase #6	$153.94	8.866%	$167.5883	$167.59	$167.60	$167.60
Purchase #7	$136.73	12.130%	$153.3153	$153.32	$153.30	$153.30
7 purchase totals =	$982.45		$1,060.2118	$1,060.22	$1,060.20	$1,060.20