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	$236.91	13.149%	$268.0613	$268.06	$268.05	$268.10
Purchase #2	$199.61	10.373%	$220.3155	$220.32	$220.30	$220.30
Purchase #3	$65.82	10.667%	$72.841	$72.84	$72.85	$72.80
Purchase #4	$63.81	5.727%	$67.4644	$67.46	$67.45	$67.50
Purchase #5	$48.27	13.353%	$54.7155	$54.72	$54.70	$54.70
Purchase #6	$239.59	10.724%	$265.2836	$265.28	$265.30	$265.30
Purchase #7	$191.61	8.297%	$207.5079	$207.51	$207.50	$207.50
7 purchase totals =	$1,045.62		$1,156.1892	$1,156.19	$1,156.15	$1,156.20