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	$58.33	7.766%	$62.8599	$62.86	$62.85	$62.90
Purchase #2	$45.40	8.412%	$49.219	$49.22	$49.20	$49.20
Purchase #3	$186.48	7.710%	$200.8576	$200.86	$200.85	$200.90
Purchase #4	$112.59	3.449%	$116.4732	$116.47	$116.45	$116.50
Purchase #5	$82.89	9.864%	$91.0663	$91.07	$91.05	$91.10
Purchase #6	$35.54	13.860%	$40.4658	$40.47	$40.45	$40.50
Purchase #7	$24.69	3.368%	$25.5216	$25.52	$25.50	$25.50
7 purchase totals =	$545.92		$586.4634	$586.47	$586.35	$586.60