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	$57.90	6.293%	$61.5436	$61.54	$61.55	$61.50
Purchase #2	$102.34	8.564%	$111.1044	$111.10	$111.10	$111.10
Purchase #3	$150.90	6.523%	$160.7432	$160.74	$160.75	$160.70
Purchase #4	$38.92	10.461%	$42.9914	$42.99	$43.00	$43.00
Purchase #5	$48.85	13.844%	$55.6128	$55.61	$55.60	$55.60
Purchase #6	$187.60	12.216%	$210.5172	$210.52	$210.50	$210.50
Purchase #7	$48.69	9.863%	$53.4923	$53.49	$53.50	$53.50
7 purchase totals =	$635.20		$696.0049	$695.99	$696.00	$695.90