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	$50.64	7.537%	$54.4567	$54.46	$54.45	$54.50
Purchase #2	$206.94	10.770%	$229.2274	$229.23	$229.25	$229.20
Purchase #3	$147.52	12.542%	$166.022	$166.02	$166.00	$166.00
Purchase #4	$163.49	3.123%	$168.5958	$168.60	$168.60	$168.60
Purchase #5	$36.83	6.827%	$39.3444	$39.34	$39.35	$39.30
Purchase #6	$92.28	7.650%	$99.3394	$99.34	$99.35	$99.30
Purchase #7	$224.54	12.386%	$252.3515	$252.35	$252.35	$252.40
7 purchase totals =	$922.24		$1,009.3372	$1,009.34	$1,009.35	$1,009.30