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	$244.52	5.685%	$258.421	$258.42	$258.40	$258.40
Purchase #2	$174.45	7.412%	$187.3802	$187.38	$187.40	$187.40
Purchase #3	$20.34	8.369%	$22.0423	$22.04	$22.05	$22.00
Purchase #4	$56.85	4.827%	$59.5941	$59.59	$59.60	$59.60
Purchase #5	$130.83	10.573%	$144.6627	$144.66	$144.65	$144.70
Purchase #6	$133.31	10.752%	$147.6435	$147.64	$147.65	$147.60
Purchase #7	$239.31	9.480%	$261.9966	$262.00	$262.00	$262.00
7 purchase totals =	$999.61		$1,081.7404	$1,081.73	$1,081.75	$1,081.70