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	$34.39	7.724%	$37.0463	$37.05	$37.05	$37.00
Purchase #2	$116.39	10.493%	$128.6028	$128.60	$128.60	$128.60
Purchase #3	$168.43	9.593%	$184.5875	$184.59	$184.60	$184.60
Purchase #4	$196.78	3.873%	$204.4013	$204.40	$204.40	$204.40
Purchase #5	$202.38	3.777%	$210.0239	$210.02	$210.00	$210.00
Purchase #6	$128.52	13.634%	$146.0424	$146.04	$146.05	$146.00
Purchase #7	$100.27	7.493%	$107.7832	$107.78	$107.80	$107.80
7 purchase totals =	$947.16		$1,018.4874	$1,018.48	$1,018.50	$1,018.40