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	$235.29	3.482%	$243.4828	$243.48	$243.50	$243.50
Purchase #2	$160.29	12.582%	$180.4577	$180.46	$180.45	$180.50
Purchase #3	$7.83	12.455%	$8.8052	$8.81	$8.80	$8.80
Purchase #4	$105.59	6.629%	$112.5896	$112.59	$112.60	$112.60
Purchase #5	$227.84	5.127%	$239.5214	$239.52	$239.50	$239.50
Purchase #6	$89.31	4.468%	$93.3004	$93.30	$93.30	$93.30
Purchase #7	$169.31	9.575%	$185.5214	$185.52	$185.50	$185.50
7 purchase totals =	$995.46		$1,063.6785	$1,063.68	$1,063.65	$1,063.70