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	$74.37	5.469%	$78.4373	$78.44	$78.45	$78.40
Purchase #2	$84.64	8.329%	$91.6897	$91.69	$91.70	$91.70
Purchase #3	$187.39	4.845%	$196.469	$196.47	$196.45	$196.50
Purchase #4	$233.55	7.184%	$250.3282	$250.33	$250.35	$250.30
Purchase #5	$139.70	6.451%	$148.712	$148.71	$148.70	$148.70
Purchase #6	$246.91	5.383%	$260.2012	$260.20	$260.20	$260.20
Purchase #7	$105.60	6.667%	$112.6404	$112.64	$112.65	$112.60
7 purchase totals =	$1,072.16		$1,138.4778	$1,138.48	$1,138.50	$1,138.40