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	$152.87	10.211%	$168.4796	$168.48	$168.50	$168.50
Purchase #2	$132.97	6.140%	$141.1344	$141.13	$141.15	$141.10
Purchase #3	$141.97	8.306%	$153.762	$153.76	$153.75	$153.80
Purchase #4	$43.63	6.759%	$46.579	$46.58	$46.60	$46.60
Purchase #5	$185.33	12.687%	$208.8428	$208.84	$208.85	$208.80
Purchase #6	$73.61	12.242%	$82.6213	$82.62	$82.60	$82.60
Purchase #7	$212.29	12.139%	$238.0599	$238.06	$238.05	$238.10
7 purchase totals =	$942.67		$1,039.4790	$1,039.47	$1,039.50	$1,039.50