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	$229.70	12.793%	$259.0855	$259.09	$259.10	$259.10
Purchase #2	$65.29	5.790%	$69.0703	$69.07	$69.05	$69.10
Purchase #3	$249.69	5.190%	$262.6489	$262.65	$262.65	$262.60
Purchase #4	$40.59	4.551%	$42.4373	$42.44	$42.45	$42.40
Purchase #5	$175.48	5.849%	$185.7438	$185.74	$185.75	$185.70
Purchase #6	$38.66	13.228%	$43.7739	$43.77	$43.75	$43.80
Purchase #7	$217.35	7.432%	$233.5035	$233.50	$233.50	$233.50
7 purchase totals =	$1,016.76		$1,096.2632	$1,096.26	$1,096.25	$1,096.20