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	$190.40	5.724%	$201.2985	$201.30	$201.30	$201.30
Purchase #2	$54.70	13.246%	$61.9456	$61.95	$61.95	$61.90
Purchase #3	$85.87	3.756%	$89.0953	$89.10	$89.10	$89.10
Purchase #4	$27.27	6.237%	$28.9708	$28.97	$28.95	$29.00
Purchase #5	$81.42	9.804%	$89.4024	$89.40	$89.40	$89.40
Purchase #6	$139.89	10.429%	$154.4791	$154.48	$154.50	$154.50
Purchase #7	$121.42	10.159%	$133.7551	$133.76	$133.75	$133.80
7 purchase totals =	$700.97		$758.9468	$758.96	$758.95	$759.00