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	$192.31	6.697%	$205.189	$205.19	$205.20	$205.20
Purchase #2	$41.83	9.540%	$45.8206	$45.82	$45.80	$45.80
Purchase #3	$6.75	7.711%	$7.2705	$7.27	$7.25	$7.30
Purchase #4	$154.89	11.287%	$172.3724	$172.37	$172.35	$172.40
Purchase #5	$31.54	3.288%	$32.577	$32.58	$32.60	$32.60
Purchase #6	$211.61	6.161%	$224.6473	$224.65	$224.65	$224.60
Purchase #7	$223.97	6.555%	$238.6512	$238.65	$238.65	$238.70
7 purchase totals =	$862.90		$926.5280	$926.53	$926.50	$926.60