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	$149.49	7.604%	$160.8572	$160.86	$160.85	$160.90
Purchase #2	$148.72	11.783%	$166.2437	$166.24	$166.25	$166.20
Purchase #3	$11.81	10.617%	$13.0639	$13.06	$13.05	$13.10
Purchase #4	$30.82	8.548%	$33.4545	$33.45	$33.45	$33.50
Purchase #5	$202.49	11.224%	$225.2175	$225.22	$225.20	$225.20
Purchase #6	$96.54	4.297%	$100.6883	$100.69	$100.70	$100.70
Purchase #7	$106.30	10.413%	$117.369	$117.37	$117.35	$117.40
7 purchase totals =	$746.17		$816.8941	$816.89	$816.85	$817.00