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	$130.76	7.685%	$140.8089	$140.81	$140.80	$140.80
Purchase #2	$181.75	8.389%	$196.997	$197.00	$197.00	$197.00
Purchase #3	$56.73	4.493%	$59.2789	$59.28	$59.30	$59.30
Purchase #4	$218.36	4.330%	$227.815	$227.82	$227.80	$227.80
Purchase #5	$241.99	13.676%	$275.0846	$275.08	$275.10	$275.10
Purchase #6	$30.29	8.393%	$32.8322	$32.83	$32.85	$32.80
Purchase #7	$156.84	5.593%	$165.6121	$165.61	$165.60	$165.60
7 purchase totals =	$1,016.72		$1,098.4287	$1,098.43	$1,098.45	$1,098.40