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	$111.93	13.393%	$126.9208	$126.92	$126.90	$126.90
Purchase #2	$85.83	5.530%	$90.5764	$90.58	$90.60	$90.60
Purchase #3	$39.86	13.695%	$45.3188	$45.32	$45.30	$45.30
Purchase #4	$183.57	7.631%	$197.5782	$197.58	$197.60	$197.60
Purchase #5	$60.84	4.405%	$63.52	$63.52	$63.50	$63.50
Purchase #6	$175.86	4.369%	$183.5433	$183.54	$183.55	$183.50
Purchase #7	$212.44	8.446%	$230.3827	$230.38	$230.40	$230.40
7 purchase totals =	$870.33		$937.8402	$937.84	$937.85	$937.80