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	$227.96	13.458%	$258.6389	$258.64	$258.65	$258.60
Purchase #2	$48.47	13.372%	$54.9514	$54.95	$54.95	$55.00
Purchase #3	$159.86	13.400%	$181.2812	$181.28	$181.30	$181.30
Purchase #4	$90.64	8.384%	$98.2393	$98.24	$98.25	$98.20
Purchase #5	$247.55	3.249%	$255.5929	$255.59	$255.60	$255.60
Purchase #6	$119.54	9.139%	$130.4648	$130.46	$130.45	$130.50
Purchase #7	$201.45	7.178%	$215.9101	$215.91	$215.90	$215.90
7 purchase totals =	$1,095.47		$1,195.0786	$1,195.07	$1,195.10	$1,195.10