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	$66.85	8.520%	$72.5456	$72.55	$72.55	$72.50
Purchase #2	$56.81	5.104%	$59.7096	$59.71	$59.70	$59.70
Purchase #3	$88.31	12.860%	$99.6667	$99.67	$99.65	$99.70
Purchase #4	$186.95	9.846%	$205.3571	$205.36	$205.35	$205.40
Purchase #5	$186.47	7.516%	$200.4851	$200.49	$200.50	$200.50
Purchase #6	$229.57	11.370%	$255.6721	$255.67	$255.65	$255.70
Purchase #7	$154.68	11.360%	$172.2516	$172.25	$172.25	$172.30
7 purchase totals =	$969.64		$1,065.6878	$1,065.70	$1,065.65	$1,065.80