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	$124.91	5.183%	$131.3841	$131.38	$131.40	$131.40
Purchase #2	$248.96	4.269%	$259.5881	$259.59	$259.60	$259.60
Purchase #3	$145.54	10.689%	$161.0968	$161.10	$161.10	$161.10
Purchase #4	$144.56	6.154%	$153.4562	$153.46	$153.45	$153.50
Purchase #5	$75.50	13.655%	$85.8095	$85.81	$85.80	$85.80
Purchase #6	$59.39	9.730%	$65.1686	$65.17	$65.15	$65.20
Purchase #7	$175.30	10.308%	$193.3699	$193.37	$193.35	$193.40
7 purchase totals =	$974.16		$1,049.8732	$1,049.88	$1,049.85	$1,050.00