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	$64.55	7.846%	$69.6146	$69.61	$69.60	$69.60
Purchase #2	$15.72	7.474%	$16.8949	$16.89	$16.90	$16.90
Purchase #3	$89.78	12.389%	$100.9028	$100.90	$100.90	$100.90
Purchase #4	$13.86	13.619%	$15.7476	$15.75	$15.75	$15.70
Purchase #5	$175.50	13.651%	$199.4575	$199.46	$199.45	$199.50
Purchase #6	$230.34	12.515%	$259.1671	$259.17	$259.15	$259.20
Purchase #7	$49.31	8.370%	$53.4372	$53.44	$53.45	$53.40
7 purchase totals =	$639.06		$715.2217	$715.22	$715.20	$715.20