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	$196.49	7.176%	$210.5901	$210.59	$210.60	$210.60
Purchase #2	$85.97	5.682%	$90.8548	$90.85	$90.85	$90.90
Purchase #3	$220.99	12.357%	$248.2977	$248.30	$248.30	$248.30
Purchase #4	$184.48	7.745%	$198.768	$198.77	$198.75	$198.80
Purchase #5	$103.71	7.601%	$111.593	$111.59	$111.60	$111.60
Purchase #6	$6.92	12.781%	$7.8044	$7.80	$7.80	$7.80
Purchase #7	$54.45	3.384%	$56.2926	$56.29	$56.30	$56.30
7 purchase totals =	$853.01		$924.2006	$924.19	$924.20	$924.30