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	$105.49	3.820%	$109.5197	$109.52	$109.50	$109.50
Purchase #2	$10.78	3.563%	$11.1641	$11.16	$11.15	$11.20
Purchase #3	$39.25	9.783%	$43.0898	$43.09	$43.10	$43.10
Purchase #4	$83.71	13.613%	$95.1054	$95.11	$95.10	$95.10
Purchase #5	$127.72	3.388%	$132.0472	$132.05	$132.05	$132.00
Purchase #6	$18.96	11.234%	$21.09	$21.09	$21.10	$21.10
Purchase #7	$193.64	12.225%	$217.3125	$217.31	$217.30	$217.30
7 purchase totals =	$579.55		$629.3287	$629.33	$629.30	$629.30