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	$202.82	11.845%	$226.844	$226.84	$226.85	$226.80
Purchase #2	$103.76	7.564%	$111.6084	$111.61	$111.60	$111.60
Purchase #3	$31.63	6.223%	$33.5983	$33.60	$33.60	$33.60
Purchase #4	$205.45	4.839%	$215.3917	$215.39	$215.40	$215.40
Purchase #5	$73.61	11.316%	$81.9397	$81.94	$81.95	$81.90
Purchase #6	$24.91	10.210%	$27.4533	$27.45	$27.45	$27.50
Purchase #7	$32.72	10.568%	$36.1778	$36.18	$36.20	$36.20
7 purchase totals =	$674.90		$733.0132	$733.01	$733.05	$733.00