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	$93.56	8.618%	$101.623	$101.62	$101.60	$101.60
Purchase #2	$134.30	13.834%	$152.8791	$152.88	$152.90	$152.90
Purchase #3	$156.53	5.334%	$164.8793	$164.88	$164.90	$164.90
Purchase #4	$68.55	5.725%	$72.4745	$72.47	$72.45	$72.50
Purchase #5	$36.78	3.393%	$38.0279	$38.03	$38.05	$38.00
Purchase #6	$237.58	4.521%	$248.321	$248.32	$248.30	$248.30
Purchase #7	$224.31	5.793%	$237.3043	$237.30	$237.30	$237.30
7 purchase totals =	$951.61		$1,015.5091	$1,015.50	$1,015.50	$1,015.50