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	$47.37	12.105%	$53.1041	$53.10	$53.10	$53.10
Purchase #2	$161.48	6.603%	$172.1425	$172.14	$172.15	$172.10
Purchase #3	$32.94	10.839%	$36.5104	$36.51	$36.50	$36.50
Purchase #4	$245.82	5.182%	$258.5584	$258.56	$258.55	$258.60
Purchase #5	$138.32	7.450%	$148.6248	$148.62	$148.60	$148.60
Purchase #6	$217.68	13.415%	$246.8818	$246.88	$246.90	$246.90
Purchase #7	$117.30	11.819%	$131.1637	$131.16	$131.15	$131.20
7 purchase totals =	$960.91		$1,046.9857	$1,046.97	$1,046.95	$1,047.00