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	$140.72	7.196%	$150.8462	$150.85	$150.85	$150.80
Purchase #2	$216.85	4.469%	$226.541	$226.54	$226.55	$226.50
Purchase #3	$114.44	11.576%	$127.6876	$127.69	$127.70	$127.70
Purchase #4	$139.54	12.776%	$157.3676	$157.37	$157.35	$157.40
Purchase #5	$167.83	10.791%	$185.9405	$185.94	$185.95	$185.90
Purchase #6	$77.28	6.419%	$82.2406	$82.24	$82.25	$82.20
Purchase #7	$139.50	10.722%	$154.4572	$154.46	$154.45	$154.50
7 purchase totals =	$996.16		$1,085.0807	$1,085.09	$1,085.10	$1,085.00