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	$42.58	7.711%	$45.8633	$45.86	$45.85	$45.90
Purchase #2	$97.58	9.326%	$106.6803	$106.68	$106.70	$106.70
Purchase #3	$42.49	8.151%	$45.9534	$45.95	$45.95	$46.00
Purchase #4	$53.88	6.261%	$57.2534	$57.25	$57.25	$57.30
Purchase #5	$90.86	13.127%	$102.7872	$102.79	$102.80	$102.80
Purchase #6	$110.45	11.596%	$123.2578	$123.26	$123.25	$123.30
Purchase #7	$215.54	6.831%	$230.2635	$230.26	$230.25	$230.30
7 purchase totals =	$653.38		$712.0589	$712.05	$712.05	$712.30