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	$130.43	5.203%	$137.2163	$137.22	$137.20	$137.20
Purchase #2	$182.44	9.122%	$199.0822	$199.08	$199.10	$199.10
Purchase #3	$168.90	8.829%	$183.8122	$183.81	$183.80	$183.80
Purchase #4	$239.25	11.337%	$266.3738	$266.37	$266.35	$266.40
Purchase #5	$53.70	12.749%	$60.5462	$60.55	$60.55	$60.50
Purchase #6	$184.41	6.538%	$196.4667	$196.47	$196.45	$196.50
Purchase #7	$104.59	11.345%	$116.4557	$116.46	$116.45	$116.50
7 purchase totals =	$1,063.72		$1,159.9531	$1,159.96	$1,159.90	$1,160.00