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	$147.32	10.358%	$162.5794	$162.58	$162.60	$162.60
Purchase #2	$44.72	13.870%	$50.9227	$50.92	$50.90	$50.90
Purchase #3	$43.32	7.182%	$46.4312	$46.43	$46.45	$46.40
Purchase #4	$14.94	3.846%	$15.5146	$15.51	$15.50	$15.50
Purchase #5	$84.80	5.232%	$89.2367	$89.24	$89.25	$89.20
Purchase #6	$97.59	3.425%	$100.9325	$100.93	$100.95	$100.90
Purchase #7	$70.37	6.630%	$75.0355	$75.04	$75.05	$75.00
7 purchase totals =	$503.06		$540.6526	$540.65	$540.70	$540.50