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	$60.25	3.694%	$62.4756	$62.48	$62.50	$62.50
Purchase #2	$79.93	11.481%	$89.1068	$89.11	$89.10	$89.10
Purchase #3	$83.42	4.683%	$87.3266	$87.33	$87.35	$87.30
Purchase #4	$182.93	5.761%	$193.4686	$193.47	$193.45	$193.50
Purchase #5	$127.46	4.402%	$133.0708	$133.07	$133.05	$133.10
Purchase #6	$128.43	3.337%	$132.7157	$132.72	$132.70	$132.70
Purchase #7	$74.30	5.666%	$78.5098	$78.51	$78.50	$78.50
7 purchase totals =	$736.72		$776.6739	$776.69	$776.65	$776.70