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	$19.29	13.833%	$21.9584	$21.96	$21.95	$22.00
Purchase #2	$184.26	5.504%	$194.4017	$194.40	$194.40	$194.40
Purchase #3	$191.79	9.200%	$209.4347	$209.43	$209.45	$209.40
Purchase #4	$186.32	13.485%	$211.4453	$211.45	$211.45	$211.40
Purchase #5	$68.34	3.119%	$70.4715	$70.47	$70.45	$70.50
Purchase #6	$237.48	11.726%	$265.3269	$265.33	$265.35	$265.30
Purchase #7	$78.30	4.739%	$82.0106	$82.01	$82.00	$82.00
7 purchase totals =	$965.78		$1,055.0491	$1,055.05	$1,055.05	$1,055.00