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	$85.28	11.200%	$94.8314	$94.83	$94.85	$94.80
Purchase #2	$158.35	3.841%	$164.4322	$164.43	$164.45	$164.40
Purchase #3	$106.57	4.182%	$111.0268	$111.03	$111.05	$111.00
Purchase #4	$202.35	11.246%	$225.1063	$225.11	$225.10	$225.10
Purchase #5	$136.41	13.302%	$154.5553	$154.56	$154.55	$154.60
Purchase #6	$192.28	6.793%	$205.3416	$205.34	$205.35	$205.30
Purchase #7	$132.58	3.271%	$136.9167	$136.92	$136.90	$136.90
7 purchase totals =	$1,013.82		$1,092.2103	$1,092.22	$1,092.25	$1,092.10