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	$6.73	6.476%	$7.1658	$7.17	$7.15	$7.20
Purchase #2	$165.41	10.386%	$182.5895	$182.59	$182.60	$182.60
Purchase #3	$213.50	10.211%	$235.3005	$235.30	$235.30	$235.30
Purchase #4	$217.46	3.694%	$225.493	$225.49	$225.50	$225.50
Purchase #5	$183.77	4.136%	$191.3707	$191.37	$191.35	$191.40
Purchase #6	$167.58	4.133%	$174.5061	$174.51	$174.50	$174.50
Purchase #7	$149.78	3.520%	$155.0523	$155.05	$155.05	$155.10
7 purchase totals =	$1,104.23		$1,171.4779	$1,171.48	$1,171.45	$1,171.60