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	$128.75	11.150%	$143.1056	$143.11	$143.10	$143.10
Purchase #2	$24.63	11.835%	$27.545	$27.55	$27.55	$27.50
Purchase #3	$111.28	12.268%	$124.9318	$124.93	$124.95	$124.90
Purchase #4	$233.41	13.287%	$264.4232	$264.42	$264.40	$264.40
Purchase #5	$42.85	4.163%	$44.6338	$44.63	$44.65	$44.60
Purchase #6	$90.55	9.485%	$99.1387	$99.14	$99.15	$99.10
Purchase #7	$212.41	6.197%	$225.573	$225.57	$225.55	$225.60
7 purchase totals =	$843.88		$929.3511	$929.35	$929.35	$929.20