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	$221.92	5.195%	$233.4487	$233.45	$233.45	$233.40
Purchase #2	$167.55	7.141%	$179.5147	$179.51	$179.50	$179.50
Purchase #3	$117.53	8.635%	$127.6787	$127.68	$127.70	$127.70
Purchase #4	$228.41	10.855%	$253.2039	$253.20	$253.20	$253.20
Purchase #5	$6.70	7.187%	$7.1815	$7.18	$7.20	$7.20
Purchase #6	$77.45	7.727%	$83.4346	$83.43	$83.45	$83.40
Purchase #7	$155.85	8.685%	$169.3856	$169.39	$169.40	$169.40
7 purchase totals =	$975.41		$1,053.8477	$1,053.84	$1,053.90	$1,053.80