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	$191.60	9.399%	$209.6085	$209.61	$209.60	$209.60
Purchase #2	$164.39	3.871%	$170.7535	$170.75	$170.75	$170.80
Purchase #3	$228.66	3.373%	$236.3727	$236.37	$236.35	$236.40
Purchase #4	$77.39	8.744%	$84.157	$84.16	$84.15	$84.20
Purchase #5	$182.54	4.652%	$191.0318	$191.03	$191.05	$191.00
Purchase #6	$112.78	13.152%	$127.6128	$127.61	$127.60	$127.60
Purchase #7	$57.26	3.780%	$59.4244	$59.42	$59.40	$59.40
7 purchase totals =	$1,014.62		$1,078.9607	$1,078.95	$1,078.90	$1,079.00