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	$224.52	11.527%	$250.4004	$250.40	$250.40	$250.40
Purchase #2	$12.29	10.721%	$13.6076	$13.61	$13.60	$13.60
Purchase #3	$237.59	7.118%	$254.5017	$254.50	$254.50	$254.50
Purchase #4	$232.70	5.398%	$245.2611	$245.26	$245.25	$245.30
Purchase #5	$219.86	10.729%	$243.4488	$243.45	$243.45	$243.40
Purchase #6	$177.70	10.360%	$196.1097	$196.11	$196.10	$196.10
Purchase #7	$206.60	4.190%	$215.2565	$215.26	$215.25	$215.30
7 purchase totals =	$1,311.26		$1,418.5858	$1,418.59	$1,418.55	$1,418.60