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	$186.28	9.611%	$204.1834	$204.18	$204.20	$204.20
Purchase #2	$46.76	10.868%	$51.8419	$51.84	$51.85	$51.80
Purchase #3	$241.47	5.820%	$255.5236	$255.52	$255.50	$255.50
Purchase #4	$167.51	12.433%	$188.3365	$188.34	$188.35	$188.30
Purchase #5	$171.33	4.479%	$179.0039	$179.00	$179.00	$179.00
Purchase #6	$124.76	5.551%	$131.6854	$131.69	$131.70	$131.70
Purchase #7	$32.39	4.851%	$33.9612	$33.96	$33.95	$34.00
7 purchase totals =	$970.50		$1,044.5359	$1,044.53	$1,044.55	$1,044.50