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	$89.79	10.800%	$99.4873	$99.49	$99.50	$99.50
Purchase #2	$36.32	10.332%	$40.0726	$40.07	$40.05	$40.10
Purchase #3	$11.71	6.572%	$12.4796	$12.48	$12.50	$12.50
Purchase #4	$150.30	3.772%	$155.9693	$155.97	$155.95	$156.00
Purchase #5	$149.83	7.127%	$160.5084	$160.51	$160.50	$160.50
Purchase #6	$59.71	9.834%	$65.5819	$65.58	$65.60	$65.60
Purchase #7	$182.67	10.385%	$201.6403	$201.64	$201.65	$201.60
7 purchase totals =	$680.33		$735.7394	$735.74	$735.75	$735.80