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	$20.93	6.678%	$22.3277	$22.33	$22.35	$22.30
Purchase #2	$53.29	5.193%	$56.0573	$56.06	$56.05	$56.10
Purchase #3	$200.64	7.779%	$216.2478	$216.25	$216.25	$216.20
Purchase #4	$79.82	9.629%	$87.5059	$87.51	$87.50	$87.50
Purchase #5	$98.64	13.406%	$111.8637	$111.86	$111.85	$111.90
Purchase #6	$128.52	6.424%	$136.7761	$136.78	$136.80	$136.80
Purchase #7	$119.81	7.389%	$128.6628	$128.66	$128.65	$128.70
7 purchase totals =	$701.65		$759.4413	$759.45	$759.45	$759.50