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	$218.72	13.433%	$248.1007	$248.10	$248.10	$248.10
Purchase #2	$17.88	7.787%	$19.2723	$19.27	$19.25	$19.30
Purchase #3	$123.86	10.589%	$136.9755	$136.98	$137.00	$137.00
Purchase #4	$164.40	3.693%	$170.4713	$170.47	$170.45	$170.50
Purchase #5	$164.75	12.579%	$185.4739	$185.47	$185.45	$185.50
Purchase #6	$196.65	12.519%	$221.2686	$221.27	$221.25	$221.30
Purchase #7	$91.46	9.840%	$100.4597	$100.46	$100.45	$100.50
7 purchase totals =	$977.72		$1,082.0220	$1,082.02	$1,081.95	$1,082.20