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	$76.32	12.503%	$85.8623	$85.86	$85.85	$85.90
Purchase #2	$102.72	6.616%	$109.516	$109.52	$109.50	$109.50
Purchase #3	$75.48	9.642%	$82.7578	$82.76	$82.75	$82.80
Purchase #4	$48.56	13.725%	$55.2249	$55.22	$55.20	$55.20
Purchase #5	$124.39	8.294%	$134.7069	$134.71	$134.70	$134.70
Purchase #6	$211.90	6.319%	$225.29	$225.29	$225.30	$225.30
Purchase #7	$82.31	10.192%	$90.699	$90.70	$90.70	$90.70
7 purchase totals =	$721.68		$784.0569	$784.06	$784.00	$784.10