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	$116.56	9.215%	$127.301	$127.30	$127.30	$127.30
Purchase #2	$132.86	12.195%	$149.0623	$149.06	$149.05	$149.10
Purchase #3	$91.60	11.812%	$102.4198	$102.42	$102.40	$102.40
Purchase #4	$80.56	6.432%	$85.7416	$85.74	$85.75	$85.70
Purchase #5	$33.34	11.760%	$37.2608	$37.26	$37.25	$37.30
Purchase #6	$7.77	12.162%	$8.715	$8.72	$8.70	$8.70
Purchase #7	$227.35	5.853%	$240.6568	$240.66	$240.65	$240.70
7 purchase totals =	$690.04		$751.1573	$751.16	$751.10	$751.20