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	$134.87	10.236%	$148.6753	$148.68	$148.70	$148.70
Purchase #2	$128.34	11.695%	$143.3494	$143.35	$143.35	$143.30
Purchase #3	$156.49	7.352%	$167.9951	$168.00	$168.00	$168.00
Purchase #4	$59.55	3.125%	$61.4109	$61.41	$61.40	$61.40
Purchase #5	$145.27	5.439%	$153.1712	$153.17	$153.15	$153.20
Purchase #6	$76.84	10.838%	$85.1679	$85.17	$85.15	$85.20
Purchase #7	$126.61	12.865%	$142.8984	$142.90	$142.90	$142.90
7 purchase totals =	$827.97		$902.6682	$902.68	$902.65	$902.70