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	$138.73	8.865%	$151.0284	$151.03	$151.05	$151.00
Purchase #2	$160.97	11.521%	$179.5154	$179.52	$179.50	$179.50
Purchase #3	$108.85	12.375%	$122.3202	$122.32	$122.30	$122.30
Purchase #4	$28.45	11.167%	$31.627	$31.63	$31.65	$31.60
Purchase #5	$145.69	7.858%	$157.1383	$157.14	$157.15	$157.10
Purchase #6	$205.86	13.440%	$233.5276	$233.53	$233.55	$233.50
Purchase #7	$118.71	10.812%	$131.5449	$131.54	$131.55	$131.50
7 purchase totals =	$907.26		$1,006.7018	$1,006.71	$1,006.75	$1,006.50