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	$219.75	5.467%	$231.7637	$231.76	$231.75	$231.80
Purchase #2	$8.27	6.537%	$8.8106	$8.81	$8.80	$8.80
Purchase #3	$162.37	10.810%	$179.9222	$179.92	$179.90	$179.90
Purchase #4	$80.70	10.307%	$89.0177	$89.02	$89.00	$89.00
Purchase #5	$47.30	9.285%	$51.6918	$51.69	$51.70	$51.70
Purchase #6	$124.77	13.861%	$142.0644	$142.06	$142.05	$142.10
Purchase #7	$77.66	6.481%	$82.6931	$82.69	$82.70	$82.70
7 purchase totals =	$720.82		$785.9635	$785.95	$785.90	$786.00