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	$150.70	7.613%	$162.1728	$162.17	$162.15	$162.20
Purchase #2	$80.83	10.433%	$89.263	$89.26	$89.25	$89.30
Purchase #3	$98.73	4.716%	$103.3861	$103.39	$103.40	$103.40
Purchase #4	$192.60	8.236%	$208.4625	$208.46	$208.45	$208.50
Purchase #5	$146.73	7.566%	$157.8316	$157.83	$157.85	$157.80
Purchase #6	$248.72	9.437%	$272.1917	$272.19	$272.20	$272.20
Purchase #7	$77.91	7.240%	$83.5507	$83.55	$83.55	$83.60
7 purchase totals =	$996.22		$1,076.8584	$1,076.85	$1,076.85	$1,077.00