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	$110.80	11.779%	$123.8511	$123.85	$123.85	$123.90
Purchase #2	$103.98	7.155%	$111.4198	$111.42	$111.40	$111.40
Purchase #3	$52.64	5.277%	$55.4178	$55.42	$55.40	$55.40
Purchase #4	$149.53	9.218%	$163.3137	$163.31	$163.30	$163.30
Purchase #5	$202.88	13.171%	$229.6013	$229.60	$229.60	$229.60
Purchase #6	$239.70	6.143%	$254.4248	$254.42	$254.40	$254.40
Purchase #7	$123.81	6.396%	$131.7289	$131.73	$131.75	$131.70
7 purchase totals =	$983.34		$1,069.7574	$1,069.75	$1,069.70	$1,069.70