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	$143.28	4.364%	$149.5327	$149.53	$149.55	$149.50
Purchase #2	$53.54	10.318%	$59.0643	$59.06	$59.05	$59.10
Purchase #3	$73.53	10.707%	$81.4029	$81.40	$81.40	$81.40
Purchase #4	$84.48	8.364%	$91.5459	$91.55	$91.55	$91.50
Purchase #5	$53.59	5.594%	$56.5878	$56.59	$56.60	$56.60
Purchase #6	$166.92	11.167%	$185.56	$185.56	$185.55	$185.60
Purchase #7	$226.41	13.703%	$257.435	$257.44	$257.45	$257.40
7 purchase totals =	$801.75		$881.1286	$881.13	$881.15	$881.10