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	$225.53	3.499%	$233.4213	$233.42	$233.40	$233.40
Purchase #2	$88.68	11.136%	$98.5554	$98.56	$98.55	$98.60
Purchase #3	$31.38	10.680%	$34.7314	$34.73	$34.75	$34.70
Purchase #4	$51.89	5.136%	$54.5551	$54.56	$54.55	$54.60
Purchase #5	$138.98	4.786%	$145.6316	$145.63	$145.65	$145.60
Purchase #6	$244.27	6.216%	$259.4538	$259.45	$259.45	$259.50
Purchase #7	$95.45	8.812%	$103.8611	$103.86	$103.85	$103.90
7 purchase totals =	$876.18		$930.2097	$930.21	$930.20	$930.30