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	$47.82	9.843%	$52.5269	$52.53	$52.55	$52.50
Purchase #2	$124.69	4.564%	$130.3809	$130.38	$130.40	$130.40
Purchase #3	$74.81	10.254%	$82.481	$82.48	$82.50	$82.50
Purchase #4	$162.77	10.186%	$179.3498	$179.35	$179.35	$179.30
Purchase #5	$128.47	11.658%	$143.447	$143.45	$143.45	$143.40
Purchase #6	$28.53	13.379%	$32.347	$32.35	$32.35	$32.30
Purchase #7	$128.32	10.426%	$141.6986	$141.70	$141.70	$141.70
7 purchase totals =	$695.41		$762.2312	$762.24	$762.30	$762.10