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	$248.49	9.498%	$272.0916	$272.09	$272.10	$272.10
Purchase #2	$131.30	8.195%	$142.06	$142.06	$142.05	$142.10
Purchase #3	$155.61	10.540%	$172.0113	$172.01	$172.00	$172.00
Purchase #4	$172.98	13.841%	$196.9222	$196.92	$196.90	$196.90
Purchase #5	$239.69	10.378%	$264.565	$264.57	$264.55	$264.60
Purchase #6	$31.83	12.788%	$35.9004	$35.90	$35.90	$35.90
Purchase #7	$145.76	8.801%	$158.5883	$158.59	$158.60	$158.60
7 purchase totals =	$1,125.66		$1,242.1388	$1,242.14	$1,242.10	$1,242.20