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	$35.58	5.550%	$37.5547	$37.55	$37.55	$37.60
Purchase #2	$80.62	6.367%	$85.7531	$85.75	$85.75	$85.80
Purchase #3	$210.30	6.345%	$223.6435	$223.64	$223.65	$223.60
Purchase #4	$150.50	9.143%	$164.2602	$164.26	$164.25	$164.30
Purchase #5	$149.60	4.288%	$156.0148	$156.01	$156.00	$156.00
Purchase #6	$223.79	13.627%	$254.2859	$254.29	$254.30	$254.30
Purchase #7	$109.32	7.436%	$117.449	$117.45	$117.45	$117.40
7 purchase totals =	$959.71		$1,038.9612	$1,038.95	$1,038.95	$1,039.00