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	$125.48	13.176%	$142.0132	$142.01	$142.00	$142.00
Purchase #2	$60.37	6.755%	$64.448	$64.45	$64.45	$64.40
Purchase #3	$160.77	4.394%	$167.8342	$167.83	$167.85	$167.80
Purchase #4	$203.32	10.476%	$224.6198	$224.62	$224.60	$224.60
Purchase #5	$29.73	6.617%	$31.6972	$31.70	$31.70	$31.70
Purchase #6	$186.75	4.161%	$194.5207	$194.52	$194.50	$194.50
Purchase #7	$144.27	4.872%	$151.2988	$151.30	$151.30	$151.30
7 purchase totals =	$910.69		$976.4319	$976.43	$976.40	$976.30