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	$49.91	10.874%	$55.3372	$55.34	$55.35	$55.30
Purchase #2	$16.75	7.813%	$18.0587	$18.06	$18.05	$18.10
Purchase #3	$77.39	4.353%	$80.7588	$80.76	$80.75	$80.80
Purchase #4	$214.55	11.157%	$238.4873	$238.49	$238.50	$238.50
Purchase #5	$237.33	11.342%	$264.248	$264.25	$264.25	$264.20
Purchase #6	$247.98	9.632%	$271.8654	$271.87	$271.85	$271.90
Purchase #7	$166.27	8.657%	$180.664	$180.66	$180.65	$180.70
7 purchase totals =	$1,010.18		$1,109.4194	$1,109.43	$1,109.40	$1,109.50