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	$175.48	5.116%	$184.4576	$184.46	$184.45	$184.50
Purchase #2	$213.56	11.571%	$238.271	$238.27	$238.25	$238.30
Purchase #3	$229.60	6.602%	$244.7582	$244.76	$244.75	$244.80
Purchase #4	$18.68	11.618%	$20.8502	$20.85	$20.85	$20.90
Purchase #5	$127.55	13.530%	$144.8075	$144.81	$144.80	$144.80
Purchase #6	$207.32	12.752%	$233.7574	$233.76	$233.75	$233.80
Purchase #7	$77.55	4.514%	$81.0506	$81.05	$81.05	$81.10
7 purchase totals =	$1,049.74		$1,147.9525	$1,147.96	$1,147.90	$1,148.20