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	$226.71	13.484%	$257.2796	$257.28	$257.30	$257.30
Purchase #2	$205.27	8.749%	$223.2291	$223.23	$223.25	$223.20
Purchase #3	$98.55	13.339%	$111.6956	$111.70	$111.70	$111.70
Purchase #4	$210.83	3.590%	$218.3988	$218.40	$218.40	$218.40
Purchase #5	$227.85	7.290%	$244.4603	$244.46	$244.45	$244.50
Purchase #6	$12.32	9.285%	$13.4639	$13.46	$13.45	$13.50
Purchase #7	$160.60	9.769%	$176.289	$176.29	$176.30	$176.30
7 purchase totals =	$1,142.13		$1,244.8163	$1,244.82	$1,244.85	$1,244.90