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	$245.93	6.447%	$261.7851	$261.79	$261.80	$261.80
Purchase #2	$174.97	7.628%	$188.3167	$188.32	$188.30	$188.30
Purchase #3	$166.76	4.209%	$173.7789	$173.78	$173.80	$173.80
Purchase #4	$22.70	12.785%	$25.6022	$25.60	$25.60	$25.60
Purchase #5	$215.34	3.277%	$222.3967	$222.40	$222.40	$222.40
Purchase #6	$129.75	11.635%	$144.8464	$144.85	$144.85	$144.80
Purchase #7	$33.73	12.198%	$37.8444	$37.84	$37.85	$37.80
7 purchase totals =	$989.18		$1,054.5704	$1,054.58	$1,054.60	$1,054.50