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	$237.33	4.310%	$247.5589	$247.56	$247.55	$247.60
Purchase #2	$61.42	10.614%	$67.9391	$67.94	$67.95	$67.90
Purchase #3	$52.96	12.462%	$59.5599	$59.56	$59.55	$59.60
Purchase #4	$149.42	11.397%	$166.4494	$166.45	$166.45	$166.40
Purchase #5	$63.68	7.702%	$68.5846	$68.58	$68.60	$68.60
Purchase #6	$240.60	8.236%	$260.4158	$260.42	$260.40	$260.40
Purchase #7	$194.27	9.130%	$212.0069	$212.01	$212.00	$212.00
7 purchase totals =	$999.68		$1,082.5146	$1,082.52	$1,082.50	$1,082.50