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	$68.32	4.815%	$71.6096	$71.61	$71.60	$71.60
Purchase #2	$16.91	6.445%	$17.9998	$18.00	$18.00	$18.00
Purchase #3	$130.67	11.247%	$145.3665	$145.37	$145.35	$145.40
Purchase #4	$195.56	11.673%	$218.3877	$218.39	$218.40	$218.40
Purchase #5	$140.99	8.382%	$152.8078	$152.81	$152.80	$152.80
Purchase #6	$30.75	10.338%	$33.9289	$33.93	$33.95	$33.90
Purchase #7	$119.32	3.203%	$123.1418	$123.14	$123.15	$123.10
7 purchase totals =	$702.52		$763.2421	$763.25	$763.25	$763.20