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	$10.70	10.864%	$11.8624	$11.86	$11.85	$11.90
Purchase #2	$90.36	8.138%	$97.7135	$97.71	$97.70	$97.70
Purchase #3	$35.46	7.585%	$38.1496	$38.15	$38.15	$38.10
Purchase #4	$164.37	13.461%	$186.4958	$186.50	$186.50	$186.50
Purchase #5	$38.72	9.663%	$42.4615	$42.46	$42.45	$42.50
Purchase #6	$50.66	6.365%	$53.8845	$53.88	$53.90	$53.90
Purchase #7	$44.93	8.501%	$48.7495	$48.75	$48.75	$48.70
7 purchase totals =	$435.20		$479.3168	$479.31	$479.30	$479.30