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	$38.49	8.397%	$41.722	$41.72	$41.70	$41.70
Purchase #2	$144.67	11.687%	$161.5776	$161.58	$161.60	$161.60
Purchase #3	$83.57	7.216%	$89.6004	$89.60	$89.60	$89.60
Purchase #4	$51.51	3.621%	$53.3752	$53.38	$53.40	$53.40
Purchase #5	$98.29	10.755%	$108.8611	$108.86	$108.85	$108.90
Purchase #6	$137.28	9.473%	$150.2845	$150.28	$150.30	$150.30
Purchase #7	$16.64	7.550%	$17.8963	$17.90	$17.90	$17.90
7 purchase totals =	$570.45		$623.3171	$623.32	$623.35	$623.40