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	$239.78	9.592%	$262.7797	$262.78	$262.80	$262.80
Purchase #2	$216.76	4.543%	$226.6074	$226.61	$226.60	$226.60
Purchase #3	$49.80	9.532%	$54.5469	$54.55	$54.55	$54.50
Purchase #4	$77.49	11.544%	$86.4354	$86.44	$86.45	$86.40
Purchase #5	$82.67	8.621%	$89.797	$89.80	$89.80	$89.80
Purchase #6	$130.67	11.295%	$145.4292	$145.43	$145.45	$145.40
Purchase #7	$221.30	7.794%	$238.5481	$238.55	$238.55	$238.50
7 purchase totals =	$1,018.47		$1,104.1437	$1,104.16	$1,104.20	$1,104.00