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	$201.91	10.584%	$223.2802	$223.28	$223.30	$223.30
Purchase #2	$237.91	7.254%	$255.168	$255.17	$255.15	$255.20
Purchase #3	$80.42	11.511%	$89.6771	$89.68	$89.70	$89.70
Purchase #4	$151.86	5.665%	$160.4629	$160.46	$160.45	$160.50
Purchase #5	$137.97	5.630%	$145.7377	$145.74	$145.75	$145.70
Purchase #6	$172.77	10.692%	$191.2426	$191.24	$191.25	$191.20
Purchase #7	$183.72	6.812%	$196.235	$196.24	$196.25	$196.20
7 purchase totals =	$1,166.56		$1,261.8035	$1,261.81	$1,261.85	$1,261.80