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	$133.76	5.655%	$141.3241	$141.32	$141.30	$141.30
Purchase #2	$50.36	11.563%	$56.1831	$56.18	$56.20	$56.20
Purchase #3	$69.28	5.447%	$73.0537	$73.05	$73.05	$73.10
Purchase #4	$133.97	5.688%	$141.5902	$141.59	$141.60	$141.60
Purchase #5	$21.61	10.401%	$23.8577	$23.86	$23.85	$23.90
Purchase #6	$183.78	9.122%	$200.5444	$200.54	$200.55	$200.50
Purchase #7	$178.59	12.471%	$200.862	$200.86	$200.85	$200.90
7 purchase totals =	$771.35		$837.4152	$837.40	$837.40	$837.50