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	$151.39	5.589%	$159.8512	$159.85	$159.85	$159.90
Purchase #2	$136.78	5.640%	$144.4944	$144.49	$144.50	$144.50
Purchase #3	$168.85	8.450%	$183.1178	$183.12	$183.10	$183.10
Purchase #4	$188.96	5.127%	$198.648	$198.65	$198.65	$198.60
Purchase #5	$73.41	4.759%	$76.9036	$76.90	$76.90	$76.90
Purchase #6	$56.29	9.244%	$61.4934	$61.49	$61.50	$61.50
Purchase #7	$193.59	7.705%	$208.5061	$208.51	$208.50	$208.50
7 purchase totals =	$969.27		$1,033.0145	$1,033.01	$1,033.00	$1,033.00