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	$56.25	4.191%	$58.6074	$58.61	$58.60	$58.60
Purchase #2	$26.50	7.516%	$28.4917	$28.49	$28.50	$28.50
Purchase #3	$19.69	4.209%	$20.5188	$20.52	$20.50	$20.50
Purchase #4	$73.94	12.146%	$82.9208	$82.92	$82.90	$82.90
Purchase #5	$52.93	8.549%	$57.455	$57.46	$57.45	$57.50
Purchase #6	$109.85	11.782%	$122.7925	$122.79	$122.80	$122.80
Purchase #7	$159.25	12.209%	$178.6928	$178.69	$178.70	$178.70
7 purchase totals =	$498.41		$549.4790	$549.48	$549.45	$549.50