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	$42.49	7.476%	$45.6666	$45.67	$45.65	$45.70
Purchase #2	$233.83	8.303%	$253.2449	$253.24	$253.25	$253.20
Purchase #3	$148.40	10.537%	$164.0369	$164.04	$164.05	$164.00
Purchase #4	$72.91	7.175%	$78.1413	$78.14	$78.15	$78.10
Purchase #5	$229.75	7.299%	$246.5195	$246.52	$246.50	$246.50
Purchase #6	$57.50	5.484%	$60.6533	$60.65	$60.65	$60.70
Purchase #7	$239.69	6.441%	$255.1284	$255.13	$255.15	$255.10
7 purchase totals =	$1,024.57		$1,103.3909	$1,103.39	$1,103.40	$1,103.30