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	$30.81	10.112%	$33.9255	$33.93	$33.95	$33.90
Purchase #2	$215.68	5.199%	$226.8932	$226.89	$226.90	$226.90
Purchase #3	$82.31	8.231%	$89.0849	$89.08	$89.10	$89.10
Purchase #4	$125.37	13.737%	$142.5921	$142.59	$142.60	$142.60
Purchase #5	$167.59	3.267%	$173.0652	$173.07	$173.05	$173.10
Purchase #6	$195.83	12.828%	$220.9511	$220.95	$220.95	$221.00
Purchase #7	$212.43	13.616%	$241.3545	$241.35	$241.35	$241.40
7 purchase totals =	$1,030.02		$1,127.8665	$1,127.86	$1,127.90	$1,128.00