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	$23.87	5.370%	$25.1518	$25.15	$25.15	$25.20
Purchase #2	$127.73	8.104%	$138.0812	$138.08	$138.10	$138.10
Purchase #3	$99.31	11.863%	$111.0911	$111.09	$111.10	$111.10
Purchase #4	$240.96	3.573%	$249.5695	$249.57	$249.55	$249.60
Purchase #5	$215.65	6.434%	$229.5249	$229.52	$229.50	$229.50
Purchase #6	$148.25	10.812%	$164.2788	$164.28	$164.30	$164.30
Purchase #7	$120.94	13.132%	$136.8218	$136.82	$136.80	$136.80
7 purchase totals =	$976.71		$1,054.5191	$1,054.51	$1,054.50	$1,054.60