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	$199.79	13.390%	$226.5419	$226.54	$226.55	$226.50
Purchase #2	$147.61	11.408%	$164.4493	$164.45	$164.45	$164.40
Purchase #3	$169.90	12.298%	$190.7943	$190.79	$190.80	$190.80
Purchase #4	$77.47	3.700%	$80.3364	$80.34	$80.35	$80.30
Purchase #5	$56.34	8.731%	$61.259	$61.26	$61.25	$61.30
Purchase #6	$151.67	3.253%	$156.6038	$156.60	$156.60	$156.60
Purchase #7	$155.84	8.230%	$168.6656	$168.67	$168.65	$168.70
7 purchase totals =	$958.62		$1,048.6503	$1,048.65	$1,048.65	$1,048.60