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	$90.98	7.425%	$97.7353	$97.74	$97.75	$97.70
Purchase #2	$98.54	13.556%	$111.8981	$111.90	$111.90	$111.90
Purchase #3	$107.69	4.582%	$112.6244	$112.62	$112.60	$112.60
Purchase #4	$144.65	13.724%	$164.5018	$164.50	$164.50	$164.50
Purchase #5	$110.35	11.469%	$123.006	$123.01	$123.00	$123.00
Purchase #6	$65.74	13.735%	$74.7694	$74.77	$74.75	$74.80
Purchase #7	$220.77	13.865%	$251.3798	$251.38	$251.40	$251.40
7 purchase totals =	$838.72		$935.9148	$935.92	$935.90	$935.90