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	$108.51	13.209%	$122.8431	$122.84	$122.85	$122.80
Purchase #2	$106.54	10.826%	$118.074	$118.07	$118.05	$118.10
Purchase #3	$90.81	12.670%	$102.3156	$102.32	$102.30	$102.30
Purchase #4	$64.67	11.834%	$72.323	$72.32	$72.30	$72.30
Purchase #5	$225.72	5.439%	$237.9969	$238.00	$238.00	$238.00
Purchase #6	$58.59	6.727%	$62.5313	$62.53	$62.55	$62.50
Purchase #7	$216.62	7.811%	$233.5402	$233.54	$233.55	$233.50
7 purchase totals =	$871.46		$949.6241	$949.62	$949.60	$949.50