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	$227.67	10.218%	$250.9333	$250.93	$250.95	$250.90
Purchase #2	$104.62	6.154%	$111.0583	$111.06	$111.05	$111.10
Purchase #3	$97.30	10.440%	$107.4581	$107.46	$107.45	$107.50
Purchase #4	$158.78	9.288%	$173.5275	$173.53	$173.55	$173.50
Purchase #5	$16.26	6.430%	$17.3055	$17.31	$17.30	$17.30
Purchase #6	$74.81	4.311%	$78.0351	$78.04	$78.05	$78.00
Purchase #7	$162.76	13.331%	$184.4575	$184.46	$184.45	$184.50
7 purchase totals =	$842.20		$922.7753	$922.79	$922.80	$922.80