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	$119.83	6.705%	$127.8646	$127.86	$127.85	$127.90
Purchase #2	$213.90	10.188%	$235.6921	$235.69	$235.70	$235.70
Purchase #3	$105.55	10.328%	$116.4512	$116.45	$116.45	$116.50
Purchase #4	$247.26	7.815%	$266.5834	$266.58	$266.60	$266.60
Purchase #5	$225.60	4.750%	$236.316	$236.32	$236.30	$236.30
Purchase #6	$167.63	10.457%	$185.1591	$185.16	$185.15	$185.20
Purchase #7	$52.60	7.493%	$56.5413	$56.54	$56.55	$56.50
7 purchase totals =	$1,132.37		$1,224.6077	$1,224.60	$1,224.60	$1,224.70