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	$200.51	5.436%	$211.4097	$211.41	$211.40	$211.40
Purchase #2	$120.92	13.629%	$137.4002	$137.40	$137.40	$137.40
Purchase #3	$14.93	9.232%	$16.3083	$16.31	$16.30	$16.30
Purchase #4	$132.70	13.827%	$151.0484	$151.05	$151.05	$151.00
Purchase #5	$184.43	6.594%	$196.5913	$196.59	$196.60	$196.60
Purchase #6	$53.37	6.823%	$57.0114	$57.01	$57.00	$57.00
Purchase #7	$18.93	6.440%	$20.1491	$20.15	$20.15	$20.10
7 purchase totals =	$725.79		$789.9184	$789.92	$789.90	$789.80