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	$138.33	7.184%	$148.2676	$148.27	$148.25	$148.30
Purchase #2	$244.80	10.495%	$270.4918	$270.49	$270.50	$270.50
Purchase #3	$217.86	3.496%	$225.4764	$225.48	$225.50	$225.50
Purchase #4	$176.91	13.473%	$200.7451	$200.75	$200.75	$200.70
Purchase #5	$13.65	5.184%	$14.3576	$14.36	$14.35	$14.40
Purchase #6	$55.30	7.225%	$59.2954	$59.30	$59.30	$59.30
Purchase #7	$134.47	13.676%	$152.8601	$152.86	$152.85	$152.90
7 purchase totals =	$981.32		$1,071.4940	$1,071.51	$1,071.50	$1,071.60