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	$100.98	10.532%	$111.6152	$111.62	$111.60	$111.60
Purchase #2	$98.87	13.495%	$112.2125	$112.21	$112.20	$112.20
Purchase #3	$227.73	12.285%	$255.7066	$255.71	$255.70	$255.70
Purchase #4	$218.40	11.405%	$243.3085	$243.31	$243.30	$243.30
Purchase #5	$86.70	12.494%	$97.5323	$97.53	$97.55	$97.50
Purchase #6	$53.49	10.448%	$59.0786	$59.08	$59.10	$59.10
Purchase #7	$161.86	5.319%	$170.4693	$170.47	$170.45	$170.50
7 purchase totals =	$948.03		$1,049.9230	$1,049.93	$1,049.90	$1,049.90