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	$109.86	3.284%	$113.4678	$113.47	$113.45	$113.50
Purchase #2	$139.73	11.525%	$155.8339	$155.83	$155.85	$155.80
Purchase #3	$218.72	9.338%	$239.1441	$239.14	$239.15	$239.10
Purchase #4	$48.82	9.212%	$53.3173	$53.32	$53.30	$53.30
Purchase #5	$156.91	6.610%	$167.2818	$167.28	$167.30	$167.30
Purchase #6	$235.75	6.294%	$250.5881	$250.59	$250.60	$250.60
Purchase #7	$108.28	12.542%	$121.8605	$121.86	$121.85	$121.90
7 purchase totals =	$1,018.07		$1,101.4935	$1,101.49	$1,101.50	$1,101.50