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	$7.25	8.851%	$7.8917	$7.89	$7.90	$7.90
Purchase #2	$91.93	7.354%	$98.6905	$98.69	$98.70	$98.70
Purchase #3	$70.83	10.499%	$78.2664	$78.27	$78.25	$78.30
Purchase #4	$73.72	7.161%	$78.9991	$79.00	$79.00	$79.00
Purchase #5	$84.96	8.174%	$91.9046	$91.90	$91.90	$91.90
Purchase #6	$15.69	5.719%	$16.5873	$16.59	$16.60	$16.60
Purchase #7	$11.69	7.422%	$12.5576	$12.56	$12.55	$12.60
7 purchase totals =	$356.07		$384.8972	$384.90	$384.90	$385.00