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	$126.25	11.578%	$140.8672	$140.87	$140.85	$140.90
Purchase #2	$5.89	9.719%	$6.4624	$6.46	$6.45	$6.50
Purchase #3	$99.97	11.374%	$111.3406	$111.34	$111.35	$111.30
Purchase #4	$102.79	13.389%	$116.5526	$116.55	$116.55	$116.60
Purchase #5	$26.68	3.254%	$27.5482	$27.55	$27.55	$27.50
Purchase #6	$18.87	13.567%	$21.4301	$21.43	$21.45	$21.40
Purchase #7	$44.46	6.410%	$47.3099	$47.31	$47.30	$47.30
7 purchase totals =	$424.91		$471.5110	$471.51	$471.50	$471.50