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	$162.59	12.316%	$182.6146	$182.61	$182.60	$182.60
Purchase #2	$237.68	7.142%	$254.6551	$254.66	$254.65	$254.70
Purchase #3	$176.44	5.323%	$185.8319	$185.83	$185.85	$185.80
Purchase #4	$159.55	5.685%	$168.6204	$168.62	$168.60	$168.60
Purchase #5	$76.64	8.342%	$83.0333	$83.03	$83.05	$83.00
Purchase #6	$58.87	10.558%	$65.0855	$65.09	$65.10	$65.10
Purchase #7	$95.91	3.258%	$99.0347	$99.03	$99.05	$99.00
7 purchase totals =	$967.68		$1,038.8755	$1,038.87	$1,038.90	$1,038.80