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	$107.83	8.437%	$116.9276	$116.93	$116.95	$116.90
Purchase #2	$46.54	12.847%	$52.519	$52.52	$52.50	$52.50
Purchase #3	$84.78	5.179%	$89.1708	$89.17	$89.15	$89.20
Purchase #4	$224.43	13.828%	$255.4642	$255.46	$255.45	$255.50
Purchase #5	$26.33	7.811%	$28.3866	$28.39	$28.40	$28.40
Purchase #6	$165.82	10.151%	$182.6524	$182.65	$182.65	$182.70
Purchase #7	$67.50	13.813%	$76.8238	$76.82	$76.80	$76.80
7 purchase totals =	$723.23		$801.9444	$801.94	$801.90	$802.00