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	$215.81	3.836%	$224.0885	$224.09	$224.10	$224.10
Purchase #2	$130.31	3.174%	$134.446	$134.45	$134.45	$134.40
Purchase #3	$173.53	8.510%	$188.2974	$188.30	$188.30	$188.30
Purchase #4	$166.70	7.660%	$179.4692	$179.47	$179.45	$179.50
Purchase #5	$78.48	9.719%	$86.1075	$86.11	$86.10	$86.10
Purchase #6	$71.42	4.175%	$74.4018	$74.40	$74.40	$74.40
Purchase #7	$78.96	13.475%	$89.5999	$89.60	$89.60	$89.60
7 purchase totals =	$915.21		$976.4103	$976.42	$976.40	$976.40