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	$208.51	10.834%	$231.1	$231.10	$231.10	$231.10
Purchase #2	$212.52	5.145%	$223.4542	$223.45	$223.45	$223.50
Purchase #3	$82.29	9.709%	$90.2795	$90.28	$90.30	$90.30
Purchase #4	$99.46	5.464%	$104.8945	$104.89	$104.90	$104.90
Purchase #5	$173.95	3.374%	$179.8191	$179.82	$179.80	$179.80
Purchase #6	$230.51	13.789%	$262.295	$262.30	$262.30	$262.30
Purchase #7	$250.40	9.470%	$274.1129	$274.11	$274.10	$274.10
7 purchase totals =	$1,257.64		$1,365.9552	$1,365.95	$1,365.95	$1,366.00