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	$42.98	7.671%	$46.277	$46.28	$46.30	$46.30
Purchase #2	$193.38	9.576%	$211.8981	$211.90	$211.90	$211.90
Purchase #3	$69.82	12.311%	$78.4155	$78.42	$78.40	$78.40
Purchase #4	$213.54	5.130%	$224.4946	$224.49	$224.50	$224.50
Purchase #5	$181.32	12.427%	$203.8526	$203.85	$203.85	$203.90
Purchase #6	$12.83	4.867%	$13.4544	$13.45	$13.45	$13.50
Purchase #7	$164.36	5.826%	$173.9356	$173.94	$173.95	$173.90
7 purchase totals =	$878.23		$952.3278	$952.33	$952.35	$952.40