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	$148.86	11.127%	$165.4237	$165.42	$165.40	$165.40
Purchase #2	$40.97	10.813%	$45.4001	$45.40	$45.40	$45.40
Purchase #3	$103.96	7.852%	$112.1229	$112.12	$112.10	$112.10
Purchase #4	$31.70	13.457%	$35.9659	$35.97	$35.95	$36.00
Purchase #5	$18.50	4.264%	$19.2888	$19.29	$19.30	$19.30
Purchase #6	$31.46	7.669%	$33.8727	$33.87	$33.85	$33.90
Purchase #7	$45.94	5.256%	$48.3546	$48.35	$48.35	$48.40
7 purchase totals =	$421.39		$460.4287	$460.42	$460.35	$460.50