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	$185.83	10.768%	$205.8402	$205.84	$205.85	$205.80
Purchase #2	$116.81	7.747%	$125.8593	$125.86	$125.85	$125.90
Purchase #3	$192.68	10.853%	$213.5916	$213.59	$213.60	$213.60
Purchase #4	$105.59	10.771%	$116.9631	$116.96	$116.95	$117.00
Purchase #5	$157.30	3.468%	$162.7552	$162.76	$162.75	$162.80
Purchase #6	$6.50	11.316%	$7.2355	$7.24	$7.25	$7.20
Purchase #7	$213.56	4.451%	$223.0656	$223.07	$223.05	$223.10
7 purchase totals =	$978.27		$1,055.3105	$1,055.32	$1,055.30	$1,055.40