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	$81.47	10.705%	$90.1914	$90.19	$90.20	$90.20
Purchase #2	$148.41	3.445%	$153.5227	$153.52	$153.50	$153.50
Purchase #3	$217.72	12.485%	$244.9023	$244.90	$244.90	$244.90
Purchase #4	$163.58	8.130%	$176.8791	$176.88	$176.90	$176.90
Purchase #5	$196.40	5.136%	$206.4871	$206.49	$206.50	$206.50
Purchase #6	$9.83	8.120%	$10.6282	$10.63	$10.65	$10.60
Purchase #7	$57.90	3.528%	$59.9427	$59.94	$59.95	$59.90
7 purchase totals =	$875.31		$942.5535	$942.55	$942.60	$942.50