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	$190.81	10.429%	$210.7096	$210.71	$210.70	$210.70
Purchase #2	$198.79	12.183%	$223.0086	$223.01	$223.00	$223.00
Purchase #3	$114.59	11.295%	$127.5329	$127.53	$127.55	$127.50
Purchase #4	$57.83	3.622%	$59.9246	$59.92	$59.90	$59.90
Purchase #5	$33.96	12.440%	$38.1846	$38.18	$38.20	$38.20
Purchase #6	$52.47	5.867%	$55.5484	$55.55	$55.55	$55.50
Purchase #7	$47.88	13.287%	$54.2418	$54.24	$54.25	$54.20
7 purchase totals =	$696.33		$769.1505	$769.14	$769.15	$769.00