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	$157.70	7.538%	$169.5874	$169.59	$169.60	$169.60
Purchase #2	$190.29	3.258%	$196.4896	$196.49	$196.50	$196.50
Purchase #3	$64.54	6.531%	$68.7551	$68.76	$68.75	$68.80
Purchase #4	$48.54	9.717%	$53.2566	$53.26	$53.25	$53.30
Purchase #5	$51.61	11.709%	$57.653	$57.65	$57.65	$57.70
Purchase #6	$56.37	12.594%	$63.4692	$63.47	$63.45	$63.50
Purchase #7	$204.38	9.238%	$223.2606	$223.26	$223.25	$223.30
7 purchase totals =	$773.43		$832.4715	$832.48	$832.45	$832.70