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	$8.86	7.111%	$9.49	$9.49	$9.50	$9.50
Purchase #2	$104.50	6.624%	$111.4221	$111.42	$111.40	$111.40
Purchase #3	$39.68	9.275%	$43.3603	$43.36	$43.35	$43.40
Purchase #4	$153.27	4.327%	$159.902	$159.90	$159.90	$159.90
Purchase #5	$6.95	4.836%	$7.2861	$7.29	$7.30	$7.30
Purchase #6	$196.32	13.490%	$222.8036	$222.80	$222.80	$222.80
Purchase #7	$248.96	5.561%	$262.8047	$262.80	$262.80	$262.80
7 purchase totals =	$758.54		$817.0688	$817.06	$817.05	$817.10