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	$109.74	6.538%	$116.9148	$116.91	$116.90	$116.90
Purchase #2	$98.30	5.628%	$103.8323	$103.83	$103.85	$103.80
Purchase #3	$146.84	13.814%	$167.1245	$167.12	$167.10	$167.10
Purchase #4	$192.31	13.603%	$218.4699	$218.47	$218.45	$218.50
Purchase #5	$145.59	10.783%	$161.289	$161.29	$161.30	$161.30
Purchase #6	$174.37	8.396%	$189.0101	$189.01	$189.00	$189.00
Purchase #7	$213.86	5.536%	$225.6993	$225.70	$225.70	$225.70
7 purchase totals =	$1,081.01		$1,182.3399	$1,182.33	$1,182.30	$1,182.30