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	$210.42	10.478%	$232.4678	$232.47	$232.45	$232.50
Purchase #2	$158.76	3.667%	$164.5817	$164.58	$164.60	$164.60
Purchase #3	$155.28	7.737%	$167.294	$167.29	$167.30	$167.30
Purchase #4	$147.53	8.775%	$160.4758	$160.48	$160.50	$160.50
Purchase #5	$105.70	8.124%	$114.2871	$114.29	$114.30	$114.30
Purchase #6	$48.47	9.128%	$52.8943	$52.89	$52.90	$52.90
Purchase #7	$123.30	10.560%	$136.3205	$136.32	$136.30	$136.30
7 purchase totals =	$949.46		$1,028.3212	$1,028.32	$1,028.35	$1,028.40