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	$179.80	13.228%	$203.5839	$203.58	$203.60	$203.60
Purchase #2	$142.56	9.378%	$155.9293	$155.93	$155.95	$155.90
Purchase #3	$232.35	9.856%	$255.2504	$255.25	$255.25	$255.30
Purchase #4	$145.38	13.693%	$165.2869	$165.29	$165.30	$165.30
Purchase #5	$35.50	6.264%	$37.7237	$37.72	$37.70	$37.70
Purchase #6	$161.82	5.723%	$171.081	$171.08	$171.10	$171.10
Purchase #7	$106.92	11.153%	$118.8448	$118.84	$118.85	$118.80
7 purchase totals =	$1,004.33		$1,107.7000	$1,107.69	$1,107.75	$1,107.70