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	$170.95	13.555%	$194.1223	$194.12	$194.10	$194.10
Purchase #2	$217.66	13.271%	$246.5457	$246.55	$246.55	$246.50
Purchase #3	$162.56	6.727%	$173.4954	$173.50	$173.50	$173.50
Purchase #4	$208.28	5.208%	$219.1272	$219.13	$219.15	$219.10
Purchase #5	$145.33	13.464%	$164.8972	$164.90	$164.90	$164.90
Purchase #6	$197.71	12.548%	$222.5187	$222.52	$222.50	$222.50
Purchase #7	$92.47	9.143%	$100.9245	$100.92	$100.90	$100.90
7 purchase totals =	$1,194.96		$1,321.6310	$1,321.64	$1,321.60	$1,321.50