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	$210.95	9.552%	$231.0999	$231.10	$231.10	$231.10
Purchase #2	$10.92	12.449%	$12.2794	$12.28	$12.30	$12.30
Purchase #3	$41.88	10.835%	$46.4177	$46.42	$46.40	$46.40
Purchase #4	$15.46	13.423%	$17.5352	$17.54	$17.55	$17.50
Purchase #5	$196.91	5.654%	$208.0433	$208.04	$208.05	$208.00
Purchase #6	$112.54	10.650%	$124.5255	$124.53	$124.55	$124.50
Purchase #7	$79.89	3.408%	$82.6127	$82.61	$82.60	$82.60
7 purchase totals =	$668.55		$722.5137	$722.52	$722.55	$722.40