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	$73.76	12.266%	$82.8074	$82.81	$82.80	$82.80
Purchase #2	$190.72	10.774%	$211.2682	$211.27	$211.25	$211.30
Purchase #3	$86.53	5.385%	$91.1896	$91.19	$91.20	$91.20
Purchase #4	$97.34	12.421%	$109.4306	$109.43	$109.45	$109.40
Purchase #5	$54.64	10.495%	$60.3745	$60.37	$60.35	$60.40
Purchase #6	$225.78	3.530%	$233.75	$233.75	$233.75	$233.80
Purchase #7	$148.68	9.195%	$162.3511	$162.35	$162.35	$162.40
7 purchase totals =	$877.45		$951.1714	$951.17	$951.15	$951.30