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	$41.79	13.482%	$47.4241	$47.42	$47.40	$47.40
Purchase #2	$176.51	3.530%	$182.7408	$182.74	$182.75	$182.70
Purchase #3	$233.82	8.788%	$254.3681	$254.37	$254.35	$254.40
Purchase #4	$143.63	12.796%	$162.0089	$162.01	$162.00	$162.00
Purchase #5	$166.63	11.309%	$185.4742	$185.47	$185.45	$185.50
Purchase #6	$170.61	12.202%	$191.4278	$191.43	$191.45	$191.40
Purchase #7	$40.72	10.194%	$44.871	$44.87	$44.85	$44.90
7 purchase totals =	$973.71		$1,068.3149	$1,068.31	$1,068.25	$1,068.30