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	$235.75	6.490%	$251.0502	$251.05	$251.05	$251.10
Purchase #2	$75.30	4.230%	$78.4852	$78.49	$78.50	$78.50
Purchase #3	$13.73	9.829%	$15.0795	$15.08	$15.10	$15.10
Purchase #4	$24.53	13.727%	$27.8972	$27.90	$27.90	$27.90
Purchase #5	$127.53	13.257%	$144.4367	$144.44	$144.45	$144.40
Purchase #6	$196.29	10.821%	$217.5305	$217.53	$217.55	$217.50
Purchase #7	$128.25	10.215%	$141.3507	$141.35	$141.35	$141.40
7 purchase totals =	$801.38		$875.8300	$875.84	$875.90	$875.90