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	$127.28	9.773%	$139.7191	$139.72	$139.70	$139.70
Purchase #2	$10.51	5.710%	$11.1101	$11.11	$11.10	$11.10
Purchase #3	$12.38	6.498%	$13.1845	$13.18	$13.20	$13.20
Purchase #4	$232.46	6.690%	$248.0116	$248.01	$248.00	$248.00
Purchase #5	$100.65	11.691%	$112.417	$112.42	$112.40	$112.40
Purchase #6	$38.69	10.873%	$42.8968	$42.90	$42.90	$42.90
Purchase #7	$128.58	7.292%	$137.9561	$137.96	$137.95	$138.00
7 purchase totals =	$650.55		$705.2952	$705.30	$705.25	$705.30