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	$214.83	3.619%	$222.6047	$222.60	$222.60	$222.60
Purchase #2	$174.63	12.703%	$196.8132	$196.81	$196.80	$196.80
Purchase #3	$206.95	6.197%	$219.7747	$219.77	$219.75	$219.80
Purchase #4	$170.87	9.274%	$186.7165	$186.72	$186.70	$186.70
Purchase #5	$143.50	5.152%	$150.8931	$150.89	$150.90	$150.90
Purchase #6	$74.67	5.592%	$78.8455	$78.85	$78.85	$78.80
Purchase #7	$230.83	3.817%	$239.6408	$239.64	$239.65	$239.60
7 purchase totals =	$1,216.28		$1,295.2885	$1,295.28	$1,295.25	$1,295.20