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	$201.84	10.267%	$222.5629	$222.56	$222.55	$222.60
Purchase #2	$176.27	11.779%	$197.0328	$197.03	$197.05	$197.00
Purchase #3	$53.72	6.382%	$57.1484	$57.15	$57.15	$57.10
Purchase #4	$41.33	3.826%	$42.9113	$42.91	$42.90	$42.90
Purchase #5	$48.67	8.685%	$52.897	$52.90	$52.90	$52.90
Purchase #6	$5.78	8.336%	$6.2618	$6.26	$6.25	$6.30
Purchase #7	$225.59	4.874%	$236.5853	$236.59	$236.60	$236.60
7 purchase totals =	$753.20		$815.3995	$815.40	$815.40	$815.40