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	$105.78	8.560%	$114.8348	$114.83	$114.85	$114.80
Purchase #2	$71.29	9.213%	$77.8579	$77.86	$77.85	$77.90
Purchase #3	$206.81	12.695%	$233.0645	$233.06	$233.05	$233.10
Purchase #4	$174.70	4.616%	$182.7642	$182.76	$182.75	$182.80
Purchase #5	$43.69	12.834%	$49.2972	$49.30	$49.30	$49.30
Purchase #6	$104.67	12.570%	$117.827	$117.83	$117.85	$117.80
Purchase #7	$211.90	4.850%	$222.1772	$222.18	$222.20	$222.20
7 purchase totals =	$918.84		$997.8228	$997.82	$997.85	$997.90