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	$104.99	11.129%	$116.6743	$116.67	$116.65	$116.70
Purchase #2	$35.52	12.429%	$39.9348	$39.93	$39.95	$39.90
Purchase #3	$201.54	4.660%	$210.9318	$210.93	$210.95	$210.90
Purchase #4	$85.25	7.333%	$91.5014	$91.50	$91.50	$91.50
Purchase #5	$66.92	6.233%	$71.0911	$71.09	$71.10	$71.10
Purchase #6	$90.79	13.474%	$103.023	$103.02	$103.00	$103.00
Purchase #7	$174.31	5.222%	$183.4125	$183.41	$183.40	$183.40
7 purchase totals =	$759.32		$816.5689	$816.55	$816.55	$816.50