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	$13.83	9.475%	$15.1404	$15.14	$15.15	$15.10
Purchase #2	$143.65	12.573%	$161.7111	$161.71	$161.70	$161.70
Purchase #3	$166.26	8.834%	$180.9474	$180.95	$180.95	$180.90
Purchase #4	$86.57	4.575%	$90.5306	$90.53	$90.55	$90.50
Purchase #5	$90.77	5.802%	$96.0365	$96.04	$96.05	$96.00
Purchase #6	$148.25	5.582%	$156.5253	$156.53	$156.55	$156.50
Purchase #7	$231.51	5.620%	$244.5209	$244.52	$244.50	$244.50
7 purchase totals =	$880.84		$945.4122	$945.42	$945.45	$945.20