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	$72.81	9.177%	$79.4918	$79.49	$79.50	$79.50
Purchase #2	$82.27	7.705%	$88.6089	$88.61	$88.60	$88.60
Purchase #3	$218.72	6.859%	$233.722	$233.72	$233.70	$233.70
Purchase #4	$6.69	4.718%	$7.0056	$7.01	$7.00	$7.00
Purchase #5	$206.28	6.609%	$219.913	$219.91	$219.90	$219.90
Purchase #6	$171.29	8.827%	$186.4098	$186.41	$186.40	$186.40
Purchase #7	$206.44	11.139%	$229.4354	$229.44	$229.45	$229.40
7 purchase totals =	$964.50		$1,044.5865	$1,044.59	$1,044.55	$1,044.50