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	$151.38	3.723%	$157.0159	$157.02	$157.00	$157.00
Purchase #2	$77.83	5.712%	$82.2756	$82.28	$82.30	$82.30
Purchase #3	$99.74	3.864%	$103.594	$103.59	$103.60	$103.60
Purchase #4	$188.27	5.620%	$198.8508	$198.85	$198.85	$198.90
Purchase #5	$82.94	4.326%	$86.528	$86.53	$86.55	$86.50
Purchase #6	$178.55	11.245%	$198.6279	$198.63	$198.65	$198.60
Purchase #7	$210.36	13.686%	$239.1499	$239.15	$239.15	$239.10
7 purchase totals =	$989.07		$1,066.0421	$1,066.05	$1,066.10	$1,066.00