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	$45.86	5.118%	$48.2071	$48.21	$48.20	$48.20
Purchase #2	$78.70	5.790%	$83.2567	$83.26	$83.25	$83.30
Purchase #3	$144.59	13.795%	$164.5362	$164.54	$164.55	$164.50
Purchase #4	$13.93	6.714%	$14.8653	$14.87	$14.85	$14.90
Purchase #5	$25.64	6.672%	$27.3507	$27.35	$27.35	$27.40
Purchase #6	$55.82	11.557%	$62.2711	$62.27	$62.25	$62.30
Purchase #7	$117.42	3.513%	$121.545	$121.55	$121.55	$121.50
7 purchase totals =	$481.96		$522.0321	$522.05	$522.00	$522.10