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	$245.58	4.127%	$255.7151	$255.72	$255.70	$255.70
Purchase #2	$50.73	5.728%	$53.6358	$53.64	$53.65	$53.60
Purchase #3	$107.85	9.342%	$117.9253	$117.93	$117.95	$117.90
Purchase #4	$243.40	11.577%	$271.5784	$271.58	$271.60	$271.60
Purchase #5	$228.64	4.756%	$239.5141	$239.51	$239.50	$239.50
Purchase #6	$180.27	8.775%	$196.0887	$196.09	$196.10	$196.10
Purchase #7	$218.80	4.768%	$229.2324	$229.23	$229.25	$229.20
7 purchase totals =	$1,275.27		$1,363.6898	$1,363.70	$1,363.75	$1,363.60